Despite the record levels of unpopularity of Congress, both parties are fielding members of the House as candidates in races that will probably determine control of the Senate.

Five of the most critical races feature a House member as the nominee: House Republicans are challenging Democratic Senate incumbents in Arkansas, Colorado and Louisiana, and House Democrats are trying to defend seats vacated by retiring Democratic senators in Iowa and Michigan.

A notable exception is Georgia, where three of the top five GOP primary candidates for the Senate were members of the House, all of whom eventually lost. Tuesday’s runoff defeat for Rep. Jack Kingston (R) was a clear example of the perils of being portrayed as a Washington insider in Senate races.

Yet party strategists contend that sitting House members have experience in fundraising and past campaigns, along with an understanding of the national issues that are in play, which trumps the potential disadvantage of being part of Washington. Primary voters in many states have demonstrated their hunger for winning the Senate majority by frequently nominating these House members by acclamation in barely contested races.

“House members are much better candidates than people who have never run for office. It’s a lot of information, so it’s hard for a novice candidate who’s never had to deal with those issues or think about how do you make hard choices, given competing principles and values,” said Sen. John Cornyn (Tex.), who chaired the National Republican Senatorial Committee from 2009 through 2012.

At least eight House members will be on Senate ballots in November, following 10 House members who were Senate nominees in 2010. This has meant that the reputedly more august “upper chamber” is certain to eclipse the record level of former House members serving. According to the Senate historical office, 51 former House members serve in the Senate, just one fewer than the 2006 level of 52.

Georgia proved to be the place where the insider label proved deadly. Republicans there sided with David Perdue, a business executive and novice politician who was chief executive of Dollar General. He now faces Democrat Michelle Nunn, a philanthropist and first-time candidate. Those House members running for Senate can expect to face a barrage of ads picking away at their voting records in the same manner Perdue used Kingston’s 22 years in the House, portraying him as someone who raised the debt ceiling and his own congressional salary.

“There’s a pretty strong anti-incumbent mood out there, and if you’re part of Washington I would generally think that can be difficult,” said Sen. Bob Corker (R-Tenn.), who won his first Senate race in 2006 by first topping former House members in his primary and then a sitting House Democrat in the general election. “But it’s even more difficult in some cases for the incumbents that are already serving in the Senate.”

Recent campaigns have brought mixed results for representatives shooting to join the Senate, particularly among Republicans. In 2012, Republicans went 1-4 in races with a sitting House member as the Senate candidate, 1-6 when including two former House members who were nominated in other races. Yet in 2010, three sitting House Republicans and two who had recently left the House won Senate races, including three previously held by Democrats.

Take Missouri. In 2010, Roy Blunt, then a veteran House Republican, ran a near-flawless campaign and won by 14 percentage points. Two years later, then-Rep. Todd Akin ran a disastrous campaign focused on social issues, losing badly to Democratic Sen. Claire McCaskill.

Four House Democrats won Senate races in 2012, but none in 2010, including two who lost by huge margins in Indiana and New Hampshire.

Sen. Sherrod Brown (D-Ohio), who defeated a Republican incumbent in 2006 after 14 years in the House, said members of the House face two distinct disadvantages running in Senate races: being tied to a congressional schedule that keeps them in Washington and building an identity with voters outside of their congressional district.

“It’s harder in a bigger state, because nobody knows you,” Brown said.

Each party’s top strategists have singled out House members as among the most underperforming candidates in Senate campaigns. Democrats have doubted the abilities of Rep. Tom Cotton (R-Ark.), a freshman lawmaker with a shining personal biography who has never won a tough campaign. At this point four years ago, John Boozman (R-Ark.), then a member of the House, had moved comfortably ahead of then-Sen. Blanche Lincoln en route to an easy victory. Today, polls show Cotton and Sen. Mark Pryor (D-Ark.) locked in a very tight race.

Republicans point to Rep. Bruce Braley (D-Iowa) as a weaker-than-expected nominee in that Senate race. A lawyer, Braley was caught on camera mocking the lack of a law degree for Sen. Charles E. Grassley (R-Iowa), who stands to become Judiciary Committee chairman if Republicans pick up the six seats they need for the majority.

Iowa is now a tossup, according to the independent Cook Political Report.

House members also can be held hostage to fractious political circumstances that now define the chamber, no matter their own position. In 2012, then-Reps. Denny Rehberg (R-Mont.) and Rick Berg (R-N.D.) faced a steady stream of questions about the House’s inability to pass a new farm bill, which was tied up in internal politics of the GOP caucus. Both lost Senate races that once appeared winnable.

This year, House GOP leaders recognized an analogous problem for two of their own running for the Senate — Kingston and Rep. Bill Cassidy (R-La.) — and pushed a flood insurance reform package that split their caucus. Both from coastal states needing the legislation, Kingston and Cassidy supported the bill’s passage.

Some House members have proven to be steady candidates this fall. Ahead for the past year, Rep. Shelley Moore Capito (R-W.Va.), a 14-year veteran of the House, has run a successful race so far and is likely to put a Democratic seat in the GOP column.

Rep. Gary Peters (D-Mich.) struggled early to expand his identity beyond the region of Detroit’s northern suburbs, but he has made no significant mistakes in a state that has tilted for Democrats in federal races for more than a decade. While the Cook report rates the race a tossup, another independent analyst, the Rothenberg Political Report, moved the race in Peters’s favor.

Democrats also say that two Republican nominees have given them fertile ground because of their membership in state legislative bodies. Joni Ernst, the GOP nominee against Braley, has three years of votes and public positions from the state Senate that Democrats are using against her, and Thom Tillis, the GOP nominee in North Carolina, is overseeing as state House speaker a brutal budget fight with fellow conservatives that has tied him down in Raleigh.

After a decade in the House, Sen. Richard Burr (R-N.C.) won his 2004 race against Erskine Bowles, a former White House chief of staff and investment banker who had never served in a legislative body. He said that lawmakers have no choice but to embrace their experience and make it “about what you accomplished,” or else the opponent will tear apart the record.

“If you can’t defend your record, you probably shouldn’t be running in the first place,” he said.