While political insiders once again will be focusing almost exclusively on today’s presidential primaries in Indiana and North Carolina, both states are holding Congressional primaries that could shake vulnerable incumbents and will set the table for competitive contests in the fall.

Perhaps the most endangered incumbent on the ballot is newly elected Rep. André Carson (Ind.), who is in a four-way Democratic primary for a full term. Carson was elected in March to fill out the term of his late grandmother, Rep. Julia Carson (D), who died in December.

Carson’s toughest competitor is former state Health Commissioner Woody Myers, who has pumped more than $1.6 million of his own funds into the race. Longtime state Reps. David Orentlicher and Carolene Mays are also running in the primary.

The primary presents a unique case for racial dynamics in the 7th district: Myers, Carson and Mays are black, while Orentlicher is not. That’s also part of the reason the presidential primary might affect the results in urban Indianapolis more than in any other primary in the state.

Obama and Carson have endorsed each other, and Obama cut a radio ad for Carson. Obama likely hopes Carson will help drive out union voters in Indianapolis, helping his statewide bid, while Carson hopes to align himself with a presidential contender who is likely to generate a huge black turnout in the district.

Although he’s been a Congressman for less than two months, Carson has enjoyed the full incumbent treatment since March. In addition to donations and appearances from many sitting Members, Carson had party support on the county, state and national level. For this and many other reasons, Carson is expected to have the edge in today’s contest.

Just east of Indianapolis in the heavily GOP 5th district, Rep. Dan Burton (R) is getting his first primary fight in many cycles. Former Marion County Coroner John McGoff (R) has charged that Burton is serving the district on autopilot.

But McGoff’s yearlong campaign is expected to fall short: The only publicly released poll, by the insider newsletter the Howey Political Report, showed Burton leading, 57 percent to 22 percent.

Nonetheless, McGoff scared Burton enough to make the incumbent spend much more than he has in the past. Burton spent $1.2 million through mid-April, compared with $817,900 on his entire re-election bid in 2006.

The 2nd district GOP primary has proven problematic for Republicans, who are trying to win the seat back from freshman Rep. Joe Donnelly (D). Although he has no chance of winning, attorney Tony Zirkle (R), a white supremacist and anti-pornography advocate, is taking some of the spotlight away from nationally recruited entrepreneur Luke Puckett (R).

Meanwhile, few surprises are likely afoot in a handful of today’s competitive North Carolina primaries, with recent polls suggesting that the frontrunners have opened wide margins.

State Sen. Kay Hagan (D) and investment adviser Jim Neal (D) are vying for a shot this fall at Sen. Elizabeth Dole (R-N.C.), who successfully drew a bye in the primary after weathering criticisms for her limited success in 2006 heading the National Republican Senatorial Committee.

In a survey released Monday, 41 percent of those interviewed picked Hagan, 11 percent chose Neal and 36 percent were undecided. The Public Policy Polling survey, conducted May 3-4, included 870 likely primary voters and had a 3.3-point margin of error.

Both candidates have spent hefty sums in the primary’s runup. Hagan had spent $1.2 million of the $1.5 million she’s raised, while Neal dropped nearly $350,000 through April 16 — $120,000 out of his own pocket.

Although Dole, a one-time icon in the Tar Heel State, is favored for re-election, some Democrats argue that the general election will be highly competitive.

After shoring up support in recent weeks and staring down credible primary opposition, Republican Reps. Walter Jones and Patrick McHenry are expected to advance to Election Day.

“The polling indicates that both of those guys are safe, although both have had strong challengers and serious races that they’ve had to work hard on,” a state Republican operative said Monday. “But … both will come out as the nominees of the party again.”

McHenry’s toughest challenger today is former Judge Advocate General Lance Sigmon (R), who has tried to capitalize — perhaps unsuccessfully — on the incumbent’s recent gaffes.

On a late March trip to Baghdad, McHenry had a high-profile run-in with a military contractor, who he termed a “two-bit security guard” to Tar Heel State Republican activists, a characterization that was caught on tape. McHenry was then chided by the Pentagon for posting video footage of his trip on his Congressional Web site.

The lawmaker later said he was sorry for posting the video on the Internet and said his characterization of the security guard was “a poor choice of words.”

A recent poll conducted by McHenry’s campaign suggests voters have accepted his apologies. In April 29-30 survey of 350 likely primary voters, McHenry appeared well out in front of Sigmon in a ballot test, 67 percent to 16 percent.

The Tel Opinion Research survey had a margin of error of 5.5 points. The poll also suggested 72 percent of voters thought the lawmaker was doing a good job.

“We’ve run a positive campaign on the Congressman’s strong record of working to promote economic growth and job creation, stopping illegal immigration, and the innovative ideas he has for lowering gas prices,” spokeswoman Rebecca Yount said in a statement. “Our opponent has a run a negative campaign based on gutter politics and character assassination. It’s obvious from this survey which message the voters prefer.”

A state GOP operative agreed with Yount’s assessment but said conservative voters in Jones’ district, too, have been forgiving, particularly on his recent conversion against the Iraq War.

“People remember the good things they’ve done for the district,” the source said. “They know the name and associate it with something good that’s been done.”

Jones faces Onslow County Commissioner Joe McLaughlin (R) on today’s ballot in a matcup that was hyped early in the cycle but failed to materialize — largely because McLaughlin raised only $122,000 to help his cause.