U.S. Rep. Leonard Boswell, D-Iowa, left, talks with U.S. Rep. Tom Latham, R-Iowa, during a rally in Des Moines on May 7, 2010, calling for greater spending on construction projects in order to improve the state's economy. (AP Photo/Charlie Neibergall) (Charlie Neibergall/AP)

In 1996, two years into the Gingrich Revolution, retired Army Lt. Col. Leonard L. Boswell narrowly won a seat in Congress to become the only Democrat in Iowa’s five-member House delegation. His margin of victory, 49 percent to 48 percent while Bill Clinton was trouncing Robert J. Dole by 10 points, established him as a vulnerable incumbent and made him a perennial GOP target over the next decade and a half.

For 10 years, Boswell remained the only Iowa Democrat in the House and, against the odds, has been reelected seven times.

But at 78, he acknowledges that 2012 will be his toughest test yet. That’s because he is seeking reelection in a newly drawn 3rd Congressional District, against a Republican candidate in a race that is important to the GOP House leadership and which is attracting huge amounts of attention and money because Iowa is so crucial to the outcome of the presidential election.

Iowa lost one of its five House seats after the 2010 reapportionment, and as a consequence of the redistricting that followed, Boswell in the fall will face Rep. Tom Latham, who currently represents the neighboring 4th District and is a close friend of House Speaker John A. Boehner (R-Ohio).

“There’s no way I’m going to match the three people I’m running against,” Boswell said in a recent interview at his Des Moines office in between fundraising phone calls. “You know I’m running against three people, don’t you?” he said with a slight chuckle. “I’m running against Latham, I think I’m running against Boehner, and there’s this guy called Karl Rove.”

Latham is Boswell’s best-funded, most experienced opponent ever, while former White House adviser Rove’s super PAC, Crossroads GPS, has spent more than $500,000 attacking Boswell with several television ads since last summer. And Bos­well thinks that some of his former donors — mostly lobbyists and PACs tied to large companies and trade associations — have been pressured by Boehner to withhold as much as $400,000 this year. Previous supporters aren’t writing checks, Boswell said, because “they want to influence the speaker and his best friend.”

Latham, who moved south from his old north-central Iowa district to challenge Bos­well, said he was unaware of the speaker pressuring donors. “I’m sure people make decisions as to who they support, so that’s up to them.”

Cory Fritz, a Boehner spokesman, dismissed the allegation, saying that Boswell should worry more about “his anti-business record . . . instead of ginning up absurd conspiracy theories.”

The new 3rd District stretches from Des Moines west to Council Bluffs and is the most evenly divided district in the state. It has the fewest registered independent voters, and Republicans maintain a narrow 6,000-voter advantage over Democrats.

“It is the swingiest, most-even congressional district in the swingiest of swing states, right smack in the middle of the country,” said Sue Dvorsky, chair of the Iowa Democratic Party.

Elected in 1994 — the year that Boehner was deputized to oversee the crafting of the GOP’s “Contract With America” — Latham became fast friends with the Ohio Republican.

Along with Sens. Saxby Chambliss (R-Ga.) and Richard Burr (R-N.C.), Latham and Boehner have held regular supper clubs all over Washington since the mid-1990s, with Barracks Row restaurants near the Navy Yard as their most regular haunts.

Every August of an election year, Boehner heads out in an RV across the Midwest stumping for GOP candidates, a trek that almost invariably includes a stop in Latham’s home for some downtime.

Latham is close enough to Boehner that the speaker gives him open-door credentials. He also serves as an early-warning system, picking up intelligence of trouble brewing inside the GOP conference and relaying it to Boehner.

Despite this close friendship — or perhaps because of it — Latham has freedom to vote as he pleases. In 2008, while still minority leader, Boehner could muster only a third of his conference to support the Wall Street bailout as it went down in flames. Latham voted no, as he did later that same week on a do-over vote that passed. Last August, in the most important vote of Boehner’s speakership, on whether to raise the federal debt ceiling, Latham was among the 66 Republicans who voted no.

In an interview, Latham played down his close relationship with Boehner, calling it “just a personal friendship” and noting that they have daughters of a similar age.

“As far as being relevant in the race, I don’t think [House Minority Leader] Nancy Pelosi or Boehner will have an effect,” Latham said.

Democrats, eager to protect Boswell, have named him to a list of 15 vulnerable incumbents whom they plan to help with money and manpower. And the House Majority PAC, a Democrat-aligned group, is running ads that label Latham as “Wrong for Medicare,” some of which feature images of him alongside Boehner.

Latham said such attacks won’t work: “People get it today. They know that stuff is not sustainable. They know that if nothing is done that it’s going to go bankrupt. I think that person who actually proposes things, who will save Medicare will be in a lot stronger position than someone who demagogues the issue.”

Latham said he plans to force Boswell to defend his support of President Obama’s policies. “He voted for the stimulus package, I voted against it,” Latham said. “He voted for cap and trade, I voted against it. He voted for the health-care bill, I voted against it. He voted for Dodd-Frank.”

Although Latham is a virtual unknown across much of the district, the National Republican Congressional Committee considers him the best-organized GOP incumbent and credits him for recruiting precinct captains early in the race. Latham’s campaign raised more than $400,000 in the first three months of this year, and he has about $2 million available to spend.

Boswell has struggled to keep pace — he raised roughly $213,000 in the first quarter and had about $644,000 in the bank. Records show his financial support shrinking.

AT&T donated $10,000 to Boswell in 2010, but the telecommunications giant has given him half that this year; Latham received $10,000 for both cycles. The National Air Traffic Controllers Association has not donated to Boswell this cycle after giving him $10,000 in 2010; Latham received $10,000 from the union this cycle, up from $4,500 in 2010.

The National Rifle Association gives Boswell high marks for his support of gun rights, but the group hasn’t donated to him this year after giving him $7,950 in 2010. Latham received $3,000 for his 2012 race.

Other groups — the American Physical Therapy Association, Verizon Communications, Honeywell International and the Chicago Mercantile Exchange, have given less or nothing at all to Boswell, while funneling money to Latham.

Most donors declined to comment, but some organizations said the nature of the unique matchup between two sitting lawmakers — and not pressure from Boehner — required them to choose sides.

“We have friends running against friends in many states, including Iowa,” said Dave Warner, a spokesman for the National Pork Producers Council. The group gave Boswell $9,000 in 2010 but doesn’t plan to donate to him this year. Latham received $5,000 from the group, down from $8,000 in 2010.

“We’ve had to take a hard look at where members of Congress are on our issues,” Warner said, adding that ultimately Latham has been more supportive to pork producers.

Harold Schaitberger, president of the International Association of Firefighters, called Boswell a friend but said Latham “went above and beyond” what was expected of him as a Republican lawmaker to support federal firefighting funds. To that end, Latham received $5,000 from the union this year; Boswell received just $1,000, down from $10,000 in 2010.

No matter who his opponent’s friends are, Boswell is accustomed to competitive contests: “It seems like it’s been that way my entire life.”

“It just means you have to get out and hustle a little harder,” he added. “That’s what I’m used to.”

Staff writers Paul Kane and T.W. Farnam contributed to this report.