With just a little more than three weeks to go before the Iowa caucuses, the presidential race for Congressional endorsements has entered its final frenzy.

[IMGCAP(1)]The last two endorsements from the Iowa House delegation were snatched up by Sen. Barack Obama (D-Ill.) and former Sen. Fred Thompson (R-Tenn.) on Monday.

Obama snagged the support of freshman Rep. Dave Loebsack (D), while Thompson was the last-minute choice of Rep. Steve King (R).

Loebsack called Obama the strongest candidate in the Democratic field.

“He’s building the kind of grassroots movement that will not just make him the most electable Democrat in a general election, but will help him enter the

White House with a mandate for change that Washington can’t ignore,” Loebsack said in a statement released by the Obama campaign.

Loebsack’s move means that the Hawkeye State’s three Democratic House Members are each backing a different Democratic frontrunner. Rep. Leonard Boswell announced last week that he is with Sen. Hillary Rodham Clinton (N.Y.), and Rep. Bruce Braley announced earlier that he is supporting former Sen. John Edwards (N.C.).

King, who was believed to be headed toward endorsing former Massachusetts Gov. Mitt Romney (R) before going public with his support for Thompson, is among the leading voices on the issue of illegal immigration in Congress.

The last member of the Iowa House delegation, Rep. Tom Latham (R), has vowed to stay neutral through the primary.

Also on Monday, Sen. John McCain (R-Ariz.) picked up the backing of Sen. Joe Lieberman (Conn.), an Independent who caucuses with Democrats. McCain’s campaign hopes Lieberman’s support will help him win over independent voters in New Hampshire, who can choose which party primary to participate in.

Lieberman said that the extraordinary times called for him to step forward and cross political lines.

“In this critical election, no one should let party lines be a barrier to choosing the person we believe is best qualified to lead our nation forward,” Lieberman said. “The problems that confront us are too great, the threats we face too real, and the opportunities we have too exciting for us to play partisan politics with the presidency.”

Sen. Charles Schumer (D-N.Y.) said he was disappointed that Lieberman had chosen to endorse a Republican, but he said he did not believe it signaled that a Lieberman party switch is in the offing.

“I wish he hadn’t done it,” Schumer said. “I think the needs of the American people are much more in line with the Democratic Party.”

Over the weekend, Clinton and McCain scored the key endorsements of The Des Moines Register, the largest newspaper in Iowa. Clinton also got the backing of former Sen. Bob Kerrey (D-Neb.), who has been head of The New School in New York since leaving the Senate in 2001.

Emily Pierce contributed to this report.