WASHINGTON _ The White House is hitting congressional Republicans with ever-sharper rhetorical blows as years of ill will and election-year posturing threaten to kill what was already shaping up to be a slim legislative agenda.

As the extended congressional summer break approaches, both ends of Pennsylvania Avenue are echoing with insults, catty tweets and fiery accusations.

Obama and senior administration officials have disparaged Republicans for "cowardice" on gun control, castigated GOP members they claim to have "never heard of" and accused them of being "not willing to do (their) most basic job under the Constitution."

They even have found fault with GOP-planned moments of silence for victims of the Orlando nightclub massacre, with Obama tweeting that Senate Republicans, by blocking new gun-control measures, "failed the American people."

Leading Democrats have gotten into the act, too, with Sen. Elizabeth Warren of Massachusetts accusing Republicans of deciding to "sell weapons to ISIS."

Republicans have responded with similar force. Sen. John McCain at one point accused Obama of being "directly responsible" for the June 12 Orlando massacre because of his foreign policy decisions. And some senior Republicans have hit the president hard for, in their eyes, trying to write laws that only Congress has the authority to make. One freshman senator even seemed to root for Obama's death during remarks to a religious-themed conference.

With so much venom, Obama's top spokesman didn't disagree with one reporter's assessment that his boss has lost any remaining leverage to persuade lawmakers to take up many of the issues on his final-year agenda.

Though Press Secretary Josh Earnest blamed GOP members and asserted that Obama "certainly hasn't given up," some lawmakers and longtime Washington hands say the discord bodes ill for getting anything done before the elections.

"It does concern me," said Rep. John Lewis of Georgia, who led House Democrats in a chamber sit-in that lasted more than 25 hours. Lewis may have contributed to the bad blood by labeling House Republicans' tactics "extremely unfair and toxic."

"I think it is ramping up," he said. "I was hoping to get through this period just prior to the election with a lot of civility. (Speaker Paul D. Ryan, D-Wis. ) promised he was ushering a new era of civility _ but it seems like it's going the other way."

Republicans blame the administration for trying to score political points instead of building bridges.

"The problem with this administration is it's purely political," said Rep. Michael R. Turner, R-Ohio, a senior Armed Services Committee member. "Here we are at the end of the administration, the president should be looking to Congress for common ground on the things that can be done. But all they look for is political advantage.

"The president is campaigning on the presidential campaign and he's not up for re-election," Turner said. "He needs to get behind his desk in the Oval Office and do some work."

Turner took issue with Earnest's June 14 criticism of "some Republican congressman I've never heard of" complaining on cable news about Obama's refusal to use the term "radical Islamic extremism." Earlier the same day, Obama issued a blistering takedown of his political foes' calls for him to use the phrase, saying it contains no strategic or tactical "magic" that will defeat the Islamic State and those inspired by its ideology.

"I have always been amazed at this administration acts like this is a schoolyard and a place for name-calling as opposed to a place to do work," Turner said, clearly agitated. "But the reality is I bet they don't know names in Congress. ... This president doesn't know anybody because he doesn't do the work. He talks to television cameras and campaigns."

And then there's the Lewis-led House sit-in, which Obama and Vice President Joe Biden, both endorsed. Ryan, who was shouted down by Democrats on the House floor, is calling it a "publicity stunt." During a press conference, he read from a Democratic fundraising email sent during the floor protest. It is only fueling the bad blood.

The barrage of sharp words left Stan Collender, a former staffer for the House and Senate Budget committees, to issue this dismal prediction: "Nothing is going to get done this year.

"The rhetoric has more to do with both sides realizing nothing is going to get done, so they can be more over the top with their words," said Collender, now an executive vice president at Qorvis MSLGROUP. "It's a presidential election year, and emotions can get heated. ... And when you have a candidate like (Donald) Trump, to get people's attention, you have to raise the level of your rhetoric and be more controversial."

Still, lawmakers such as Senate Majority Whip John Cornyn, R-Texas, say the verbal back-and-forth is normal, part of the cost of doing business. Sen. Claire McCaskill, D-Mo., urges a "glass half full" perspective, saying White House officials and Republican lawmakers are still saying they want to pass a criminal justice and sentencing overhaul measure, which has broad bipartisan support, later this year.

"I don't think we can ever give up," she said. "I think everybody understands what this rhetoric is."