WASHINGTON -- Using a lawmaker's Capitol Hill committee attendance records in campaign attacks can be tricky business.

It’s a strategy that both parties have employed in recent years, with decidedly mixed results. (See: Kansas' Pat Roberts and New Hampshire's Jeanne Shaheen, who kept their jobs after such attacks in 2014, and North Carolina's Kay Hagan, who didn't.)

It's inside the Beltway-type baseball that can sometimes get technical. But it can speak to a powerful question: Whether a member of Congress is adequately representing his or her state's interests on Capitol Hill.

After weeks of hammering U.S. Sen. Johnny Isakson about his legislative record, the campaign of Democrat Jim Barksdale unveiled a new website yesterday, wheresjohnny.com. It doubles down on attacks about the Republican's committee attendance and includes links to transcripts of individual hearings he's missed over the last 11 years.

Barksdale's topline argument: Isakson missed 48 percent of hearings on the committees of which he’s been a member since arriving in the Senate in 2005.

His claim, however, is a hard one to confirm. The site doesn't include listings for the hearings Isakson did attend over the years, so one can't easily check Barksdale's numbers.

It's commonplace for lawmakers, who are often double or triple-booked, to skip hearings unless they chair the committee. (Isakson heads up the Veterans Affairs and Ethics panels. The latter was not included in Barksdale's website, as those meetings are secret, and the former lists Isakson as missing from one hearing -- in Arizona -- since he became chairman in 2015).

There's also the question about whether committee hearings are a true barometer of legislative productivity -- and how much that truly matters to Georgians, many of whom are probably watching the presidential race a whole lot more closely.

There are, of course, the final up-or-down votes on the floor to pass legislation -- the marquee votes history will remember. Isakson's missed 3.8 percent of those during his more than 11-year tenure, according to the legislative tracking site GovTrack. Committee markups could also be used as a barometer, since that's where lawmakers debate and edit legislation as they prepare it for the floor.

The truth is, however, that most legislating on Capitol Hill is done behind closed doors, which makes it hard to measure.

Isakson's campaign has fought Barksdale's characterization that he's been missing in action tooth-and-nail. They've built their ad strategy on demonstrating that Isakson can build bridges to get stuff done.

"Unfortunately, our opponent has resorted to false negative attacks," said Trey Kilpatrick, Isakson's campaign manager. "He should be a little embarrassed to use fraud, misrepresentation and half-truths to attack someone known by all to be the hardest working senator. Our opponent should be ashamed."

Barksdale's campaign, however, says attending committee hearings should be the bare minimum for a member of Congress -- and has indicated there will be plenty more of such attacks to come.

"Any U.S. senator – Democrat or Republican – ought to do the job their constituents elected them to do but Senator Isakson can’t bring himself to simply show up and say anything about Georgia at countless committee hearings," said Dave Hoffman, Barksdale’s campaign manager.