WASHINGTON -- As Democratic chances of taking back the House improve with the success of Donald Trump and Ted Cruz, party strategists are trying to figure out exactly how and where it's going to happen. It's not too difficult to see Democrats gaining 10, or even 20, seats in November, but gaining the 30 required for a majority is more difficult and will require Democrats winning a large swath of seats where Republicans are currently heavy favorites.

Winning the House majority is more than focusing on the presidential margin and allotting House seats to Democrats because of the strength of some GOP incumbents. For example, Democrats are not going to defeat Republican Rep. Frank A. LoBiondo this year, even though President Barack Obama won New Jersey's 2nd with 54 percent, or win New Jersey's 3rd (which Obama won with 52 percent), where wealthy GOP Rep. Tom MacArthur could easily outspend any challenger.

In order to take advantage of a potential presidential wave, Democratic operatives are cutting emotional ties from some rural areas that made up their previous majority, such as downstate Illinois and parts of Ohio, to focus on more suburban districts, where they believe changing demographics are moving seats into the Democratic column.

In order to win the majority, Democrats likely need to win a clear majority of a batch of 16 seats, which includes pricey plays, scenario seats, late bloomers and slippery targets.

These are not the most likely districts to flip partisan control. Democrats need to win virtually all of the seats they are currently favored to win, the pure toss-ups, and some Lean Republican seats.

For example, Democrats must win Colorado's 6th District, where Democratic state Sen. Morgan Carroll is challenging GOP Rep. Mike Coffman in a suburban district that Obama won with 52 percent in 2012. The Rothenberg & Gonzales Political Report/Roll Call recently changed the rating of Coffman's race from Lean Republican to Tilts Republican.

The majority maker districts are a collection of seats where Republicans currently have the advantage, and in some cases, the races are considered safe.

PRICEY TO PUT IN PLAY

Democrats are reaching for a quartet of districts with a well-funded Republican incumbent, and in some cases and expensive media market, which will require significant spending from Democratic outside groups to win.

Pennsylvania 7: Mitt Romney narrowly won this district in 2012, 50.4-48.5 percent, but GOP Rep. Patrick Meehan had significantly more money in the bank on April 6 than Democrats' preferred candidate, Bill Golderer, $2.5 million-$136,000. And the seat is covered by the expensive Philadelphia media market.

Arizona 2: Romney won here by an even narrower margin, 49.9-48.4 percent, but GOP Rep. Martha McSally had a $2.2 million to $389,000 cash advantage on March 31 over former Democratic state Rep. Matt Heinz.

California 10: Republican Rep. Jeff Denham had $2.4 million to $370,000 cash advantage over Democrat Michael Eggman on March 31. But Obama won the district 51-47 percent in 2012, keeping it in Democrats' sights.

California 21: Democrats can't quit going after GOP Rep. David Valadao considering Obama won the district 55-44 percent in 2012. But the congressman had a $1.1 million to $116,000 edge in campaign funds on March 31 over Democratic challenger Emilio Huerta.

SCENARIO SEATS

Utah 4: Romney won this district, 67-30 percent, in 2012, but Republican Mia Love won her initial election in 2014 by just 5 points and faced some negative headlines during her first term in office. But Love had more money on March 31 ($1.1 million to $766,000) than Democrat Doug Owens (whom she defeated last cycle) and GOP strategists won't let him skate by without a negative ad this time.

West Virginia 2: Democrats can't get over the fact that GOP Rep. Alex Mooney used to be a Republican state legislator from Maryland, and that he won his initial congressional race in 2014 by just 3 points. But Obama received just 38 percent in the district in 2012 and it's not clear Democrats will get their preferred candidate through the May 10 primary.

Montana at large: Obama received 42 percent in Montana in the last presidential race but Democrats believe GOP Rep. Ryan Zinke is vulnerable. Zinke had a $1.1 million to $524,000 cash advantage over his Democratic opponent Denise Juneau (the state superintendent of public education who came out as a lesbian at the beginning of the campaign) on March 31.

Michigan 8: Democrats didn't really challenge Republican Mike Bishop last cycle when he won here, but they won't give him a pass this time. Actress Melissa Gilbert is running in the district Romney won by just 3 points in 2012, but she trailed the congressman in campaign cash on March 31, $772,000 to $414,000, and Republicans are salivating over her opposition research book.

LATE BLOOMERS

Colorado 3: Former state Sen. Gail Schwartz jumped into the race earlier this month, but the Democrat starts off over $600,000 behind GOP Rep. Scott Tipton and Romney won the district by 6 points in 2012.

Minnesota 3: State Sen. Terri Bonoff announced her challenge to GOP Rep. Erik Paulsen in Minnesota's about 10 days ago. The good news is Obama won the suburban district narrowly in 2012. The bad news is that the congressman had $2.3 million in his campaign account on March 31.

Florida 7: Democrats are drawn to this redrawn district that Romney carried by 5 points in 2012 because they believe 12-term GOP Rep. John Mica can't handle a serious race. Their problem is that the congressman had $640,000 in the bank on March 31 and they don't have a candidate.

Kansas 3: With a focus on the suburbs, Democrats are drawn to this race, even though Romney won it by 10 points in 2012. They're also still looking for a challenger to GOP Rep. Kevin Yoder, who had $2.4 million in his campaign account on March 31.

SLIPPERY TARGETS

New York 21: Obama won here in 2012, 52-46 percent, but Republican Elise Stefanik won the open seat two years later in convincing fashion. Democrats are trying to cultivate Mike Derrick into a top-tier challenger, but he started April behind in campaign cash, $1.1 million to $225,000.

New York 23: Democrats narrowly missed defeating GOP Rep. Tom Reed in 2012, but the congressman won re-election more easily in 2014. Romney won the district by 2 points in 2012, so the district can be competitive, and Reed said some nice things about Donald Trump, but the congressman had a $1 million to $366,000 edge over Democrat John Plumb in campaign accounts on March 31.

California 25: Romney won this southern California district by just 2 points in 2012 and GOP Rep. Steve Knight has been a mediocre fundraiser. But the congressman still had twice the amount of money as his Democratic challenger, attorney Bryan Caforio, and a significant local profile thanks to his astronaut father's presence in the area.

Michigan 7: Democrats love to hate Michigan Rep. Tim Walberg and his seat looks like an enticing target, considering Obama received 48 percent in 2012 and Democrats love their candidate: state Rep. Gretchen Driskell. Walberg had more money in the bank on March 31, $1.2 million to $816,000.

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