– Amid mounting rumors of retirement, Democratic U.S. Rep. Collin Peterson says he's gearing up for another re-election run.

"I'm running 'til I'm not," said Peterson, who has represented Minnesota's Seventh Congressional District since 1991.

Republicans have hammered Peterson with attack ads for the better part of a year, hoping to drive him out of Congress.

The ink was barely dry on the 2012 election results when the National Republican Congressional Committee (NRCC), the campaign arm of House Republicans, began to air televised ads against him last April.

Peterson also was included in a series of ads the committee posted that appeared to be official websites for Democratic candidates but actually opposed their campaigns. Those ads were revamped Monday after watchdog groups complained they were misleading and now make clear that donations will be used against the Democrats, including Peterson.

Annoyed by the latest attempts to push him out, Peterson has said he's more likely to run now that Republicans are ramping up the pressure. He plans to make a final decision by early March.

"If they had left me alone, I might've retired by now," said Peterson, considered the dean of Minnesota's congressional delegation. "I guess it's just part of their harassment campaign."

For Republicans, it just makes sense to challenge Peterson in a rural, conservative-leaning district where voters have faithfully backed Republican presidential candidates for years.

Moderate record

Peterson over the years has crafted a moderate voting record that has made it tough for Republicans to paint him as a typical liberal. He took criticism from his own party for rejecting President Obama's stimulus package and for being a founding member of the Blue Dog caucus, composed of Democrats who thought their party had tilted too far left.

After a couple of narrow wins in the early- to mid-90s, Peterson typically has won his elections handily. In 2012 he won a three-way race with more than 60 percent of the vote.

Republicans say Peterson's latest challenger, GOP state Sen. Torrey Westrom of Elbow Lake, will test Peterson's mettle and voting record. Westrom's campaign is the first the NRCC has backed in more than a decade.

"I intend to represent the district [in Congress] next year," said Westrom, an attorney and 17-year state lawmaker. "If Peterson's in or out, that'll be a decision he has to make."

Beyond the farm bill

Peterson backers say his independent streak has served him well on Capitol Hill, where he has a reputation as a straight shooter more interested in progress than in politics.

As the lead Democrat on the House Agriculture Committee, Peterson toiled for years to shepherd the nearly $1 trillion farm bill through Congress.

When Obama signed the bill into law last week, Peterson opted to head home for his district in western Minnesota rather than ride to Michigan on Air Force One for an outside-the-Beltway ceremony.

"It got signed whether I was there or not," Peterson said.

Part of the GOP's plan to pick off Peterson's seat is to link him to Obama, whose poll numbers have slumped, in part, because of problems with the Affordable Care Act.

Arguing that Peterson has "waffled on Obamacare," Craig Bishop, chairman of Minnesota's Seventh District GOP, said the incumbent could be vulnerable this election cycle, especially on the health care law.

Peterson voted against the bill in 2010 but has since opposed Republican attempts to dismantle the law.

"They're trying to convince people that I somehow or another have changed my position and I haven't," Peterson said.

In a show of support, high-profile House Democrats hosted a high-priced fundraiser for Peterson in November. House Minority Leader Nancy Pelosi and Rep. Tim Walz, who represents southern Minnesota and serves on the Agriculture Committee with Peterson, were among the hosts.

"Congress as a whole is a better place because he is here," Walz said.

At least four other top Democrats on House committees have announced plans to retire or opted to run for another office. Peterson would be the fifth.

Describing the Agriculture Committee as apolitical, Peterson said having another chance to serve as chairman won't influence his final decision.

"Long-term I need to ask myself 'Am I going to be around for another farm bill?' " the 69-year-old said.

Should Peterson retire, Democrats could have a hard time defending the seat in a midterm election, said Dave Wasserman, who tracks congressional races for the Cook Political Report. Historically, the party of the president loses congressional seats during the midterms. The odds of Democrats keeping the seat would improve in 2016, a presidential election year that would bring out more young, Democratic voters to the polls, Wasserman said.

"The question is whether Peterson feels up to doing his party a favor by sticking around for at least another term," he said.

State DFL Party chair Ken Martin said the party is eyeing several potential candidates should Peterson decide to walk away, including state Sen. Kent Eken, state Reps. Andrew Falk and Paul Marquart and former state Rep. Al Juhnke.

But Martin said he has not discussed a possible 2014 congressional run with any of them. He is still banking on Peterson to stay on.

"If Collin decides not to run again, it's not because he's worried about losing a race," Martin said. "It would be because he's decided he's done what he could in Washington and it's time to leave."

Corey Mitchell is a correspondent in the Star Tribune Washington Bureau. Twitter: @C_C_Mitchell