WASHINGTON — So, to recap: In a group of primaries Tuesday night, an endangered Senate incumbent helped pick her Republican opponent, a spouse’s imprisonment failed to impede a landslide victory for a veteran House member in Michigan and a reindeer farmer/Santa impersonator is now the Republican candidate for another seat in that state.

This week has been, at least for this fleeting moment, a decidedly good one for Democrats as their preferred candidates, among their own and Republicans, won some contested primaries. Kansas, Michigan, Missouri and Washington held primaries Tuesday, and in all but Kansas, Democrats can claim success.

In Missouri, Senator Claire McCaskill, the Democratic incumbent, with her party’s help spent roughly $2 million in the Republican primary running ads calling Representative Todd Akin, one of three candidates, very conservative and lamenting that he hated debt. The Br’er Rabbit approach succeeded: Mr. Akin cruised to victory, winning 36 percent of the vote and assuring that Ms. McCaskill, while still the most endangered Senate Democrat in the country, will not have to face John Brunner, a businessman whom Republicans preferred in no small part because he would have paid for the race himself.

Now Republicans will have to spend money in a state they had all written off as theirs, and Ms. McCaskill can test whether Mr. Akin’s strong conservatism and religiosity are too much for moderate voters in her state.

Mr. Akin also defeated former State Treasurer Sarah Steelman, marking the first big defeat for Sarah Palin, who gave Ms. Steelman the nod. Ms. Palin has had a string of good luck endorsing Tea Party-tinged candidates in this election cycle, most recently boosting Ted Cruz in the Texas primary.

Testing a potential new vulnerability, the Nebraska Democratic Party will hold a news conference on Wednesday to discuss Ms. Palin’s support of Deb Fischer, the Republican candidate for Senate who seems poised to beat former Senator Bob Kerrey, the Democrat in that race.

Also in Missouri one family dynasty was dinged by another after a nasty primary fight pitting current lawmakers. Representative William Lacy Clay easily beat Representative Russ Carnahan, the son of the former governor of the state and one-time Senate candidate. It’s a wash for the party as a Democrat was always expected to prevail in the First District’s general election.

In Michigan former Representative Peter Hoekstra brushed back Clark Durant, a lawyer with a 54 percent cleanup in the Republican primary and will take on Senator Debbie Stabenow, the Democratic incumbent, as expected.

But the real action in Michigan was in the House races.

After from former Representative Thaddeus McCotter failed to qualify for the Republican ballot in Michigan’s 11th Congressional District and then resigned in embarrassment, Republicans were left with Kerry Bentivolio, a libertarian-leaning reindeer farmer and a holiday Santa, who trounced Nancy Cassis, a former state senator who formed a last-minute write-in campaign.

Democrats are now excited about their candidate, Dr. Syed Taj, a former chief of medicine at Oakwood Hospital and Medical Center in Dearborn who beat the Lyndon LaRouche-backed opponent, Bill Roberts. But the district leans Republican, so Santa Claus is (quite likely) coming to town.

Another Republican seat in the Grand Rapids area just got a little harder to hold, that of freshman Representative Justin Amash, whose claim to fame in the 112th Congress is voting no on just about every key piece of legislation, and plenty of benign measures, too. Democrats believe their winner of Tuesday’s primary, a small-business owner, Steve Pestka, gives them a fighting chance.

In the state’s one primary pitting current members of Congress, Representative Gary Peters easily defeated freshman Representative Hansen Clarke in a contest wrought by decennial Congressional redistricting.

Representative John Conyers Jr. seemed somewhat endangered entering Tuesday’s primary. But his recent travails, including but not limited to the fact his wife is serving time after being convicted of taking bribes while she was on the Detroit City Council, did not give power to his challengers. He will now almost certainly cruise to his 25th term in the House in a new district containing portions of Detroit and some neighboring suburbs.

In in the First District of Washington — where redistricting created a seat closely split between Republicans and Democrats — Democrats got their desired candidate in a former Microsoft executive, Suzan DelBene, who beat back her less-moderate Democratic opponents in a nasty and expensive primary. She now has a slight edge over Republican John Koster, in the open seat, where Representative Jay Inslee, a Democrat, resigned to run for governor.