No sitting senator has cast more votes to raise the debt limit than these five Republicans
Here's one more piece of evidence that Republicans are bluffing when they threaten to hold the debt limit hostage: 81 current senators have voted at least once to extend the debt ceiling since 2001, including all but two of the Republicans who have cast a vote at least once on the debt ceiling during that time. Seventeen current senators have not yet faced a vote on raising the debt limit.
Moreover, all five of the most prolific debt-limit raisers over the past decade are Republicans, with Olympia Snowe and Susan Collins each having voted eight times to extend the debt limit, and Dick Lugar, Mitch McConnell, and Lisa Murkowski having voted seven times apiece to do so.
Even Jim DeMint has voted to raise the debt limit. Only Mike Johanns and Jim Risch have voted against the debt limit without also voting for it. The reason? They were Republicans elected in 2008, so the votes they cast on the debt limit came when Democrats controlled both Congress and the White House, and when one party controls all of the elected branches of government, it generally must take the political responsibility of doing unpopular things like raising the debt ceiling.
It is true that nearly as many current senators (69) have voted at least once against raising the debt limit as have voted for raising it, but those "no" votes were "protest" votes, not actual efforts to block increases in the debt limit. Overall, there have been 544 votes cast in favor of raising the debt ceiling and just 322 against it. A total of 274 of the yes votes have come from Republicans, and 270 have come from Democrats, a clear demonstration of the fact that both parties have shared the responsibility for raising the debt ceiling.
These numbers are all based on nine recorded votes cast in the Senate over the past decade. I've posted a publicly available spreadsheet with all of the votes here. You can find the individual data for the votes at these links: 6/11/02, 5/23/03, 11/17/04, 3/16/06, 9/27/07, 1/28/10, 7/26/08, 10/1/08, and 2/13/09. You'll notice the final three votes (Fannie/Freddie reform, TARP, and recovery act) weren't for legislation primarily focused on raising the debt limit, but each bill did raise the debt limit. Excluding them doesn't significantly change the numbers.
Even if you exclude Freddie/Fannie, TARP, and recovery act legislation from the analysis, 78 senators voted at least once to raise the debt limit. The votes were actually closer overall, with 338 votes cast in favor of raising the debt limit, and 246 cast against it. However, the partisan split is different, because Republicans controlled the Senate and White House during three of the votes and controlled the White House for five of them. A total of 210 of the "yes" votes came from Republicans, while 128 of the "no" votes came from Democrats.
The bottom line is that no matter which set of votes you look at, never has there been a scenario where senators actually tried to block lifting the debt limit, because raising the debt limit is an unfortunate but necessary fact of life. And despite all the GOP bluster about how this time will be different, it won't be. There will be a big tug of war, and the GOP will try to force Democrats to take more than their share of the political responsibility for raising the debt limit, but this isn't a hostage situation, and this debt limit vote doesn't give Republicans any leverage to get anything of substance that they weren't already in a position to get anyway.