For many Americans, Dec. 31 might involve party-hopping, watching the ball drop in Times Square or making some short-lived resolutions and promises.

For those who operate in the political world, New Year’s Eve also is an important campaign finance deadline that spawns the kind of urgent-sounding, last-minute solicitations for political donations.

The national party committees and candidates for Congress like to bank as much money as they can by year’s end to project an image of financial strength to political opponents (and to the political reporters and pundits who analyze campaign finance documents).

One such e-mail solicitation came Wednesday from the Democratic Senatorial Campaign Committee, which is only slightly ahead of the National Republican Senatorial Committee in year-to-date fundraising despite having a 60-40 majority.

“There are less than 48 hours left until the DSCC’s crucial midnight Thursday deadline,— Executive Director J.B. Poersch wrote in red, underlined text. “Give $5 or more right now to help preserve our majority and build upon our health care success. Every dollar will make a difference in 2010.—

Sen. Mark Udall (D-Colo.) is going to bat for home-state colleague Michael Bennet (D), who faces a tough 2010 campaign to keep the seat he won by appointment in January.

In a fundraising appeal distributed by Bennet’s campaign, Udall described Bennet as “the partner I need in Washington— and also criticized Bennet’s leading opponent, former Lt. Gov. Jane Norton (R). Bennet also faces opposition in the Democratic primary from former Colorado Speaker Andrew Romanoff.

Sen. John McCain (R-Ariz.), who’s seeking a fifth term, wrote in his own solicitation that “we may not be able to continue and expand our fight for reform if I am not reelected to the U.S. Senate.—

McCain, the losing 2008 Republican presidential nominee, should face meager Democratic opposition in November but could be challenged in the GOP primary by ex-Rep. J.D. Hayworth.

As an inducement to attract contributions, party committees often promise prospective donors that their donations will be matched by Members of Congress.

House Minority Leader John Boehner (R-Ohio) wrote Wednesday on behalf of the National Republican Congressional Committee that “Republican Members of Congress have committed to doubling your impact by matching dollar-for-dollar every contribution before the end of the year.—

The next batch of campaign reports is due Jan. 31. For the national party committees, which file on a monthly basis, the reports will cover receipts and spending for December. Candidates for Congress file quarterly reports, so their finance documents will cover campaign activity for October, November and December.