The political fortunes of Betty Talmadge (in her first try for Congress) and Rep. Charles C. Diggs Jr. (in his 13th try) and a ballot proposal that would actually increase taxes should provide the most interest in primary elections being held in four states today.

Voters in Georgia, Idaho, and Michigan will choose nominees for the Senate, the House, governor, and local offices. Missouri residents will decide primary contests for House seats and local offices.

The Missouri ballot will also contain an initiative proposal that directly bucks the tax-cutting trend that seems to have swept the country in the wake of California's Proposition 13.

The plan would raise the state gasoline tax from seven to 10 cents - a 43 percent boost that would give Missouri one of the highest fuel tax rates in the nation.

The tax-raising initiative was placed on the ballot in the same way tax-cutting proposals have been put forward in several states this summer - through a broad-based petition drive. Supporters, who want the increased revenue for road repairs, have backed the plan with a heavy advertising campaign.

All 10 of Missouri's congressmen are expected to be renominated easily.

In Georgia, a close race is likely in the Democratic primary for the House seat being vacated by Rep. John J. Flynt Jr.

Betty Talmadge, whose bitter divorce from Georgia's senior senator, Herman Talmadge, has been the state's hottest item of gossip this year is competiting in a close three-way race for the nomination in Flynt's district, which encompases Atlanta's western suburbs.

Talmadge has never run for office before, but she contends that her familiarity with and contacts in Washington would make up for her inexperience. Her two chief competitors, Virginia Shappard and Peter L. Banks, are both veteran compaigners and state senators.

It seems doubtful that any of the three will get enough votes to avoid a runoff primary.

Georgia's junior senator, Sam Nunn, should have no trouble winning the Democratic nomination for a second term, but Nunn has been the target of vigorous primary compaigns by three opponents who criticize him for supporting the Panama Canal Treaties.

The primary has produced a memorable bumper sticker: "One We Had A Canal - Now We Have Nunn."

Georgia Gov. George Busbee, seems certain to win the Democratic nod for a second term.

In Michigan, too, the incumbent senator and governor should both win nominations to run for reelection this fall.

Gov. William Milliken has no opposition in the Republican gubernatorial primary.

Sen. Robert P. Griffin should easily defeat conservative L. Brooks Patterson for the GOP senatorial nomination. But Patterson has waged a spirited campaign against Griffin's absentee rate in the Senate. He offers voters $216 if they can tell him how many roll calls Griffin missed in 1977.

(The answer: 216)

Republicans like to call the Milliken-Griffin combination a "dream ticket," and both men are favored in the November election. This has undercut interest in the Democratic senatorial and gubernatorial primaries.

In the Senate race, Detroit attorney Carl Levin appears to be leading the democratic field. Former congressman Richard Vander Veen, of Grand Rapids, and Philip Power, a newcomer who has spent hundreds of thousands of his own dollars to make his name known, are Levin's chief challengers.

State Sen. William B. Fitzgerald, of Detroit, is the Democratic gubernatorial frontrunner in a four-man field. He is so confident of victory today he already has started filming commercials for the general election.

In Michigan's House primaries, Rep. Charles C. Diggs Jr., chairman of the House District Committee, seems likely to win renomination in his innercity Detroit district despite the shadow of his indictment on 35 counts of misusing congressional office funds.

Diggs has a serious primary challenger for the first time in two decades this year. But the black community that constitutes about 75 percent of the district has rallied to Diggs' side since the indictment was announced in March. Some black leaders hope to give Diggs his biggest victory margin ever to show that his constituents have not deserted him.

In Idaho, six Republicans are fighting for the nomination to challenge Gov. John Evans, who reached the governor's chair when Cecil Andrus was named interior secretary last year. Evans is unopposed in the Democratic primary.

Proposition 13 fever has become the key issue in the GOP gubernatorial contest. Idaho's own version of the tax-reduction proposal, known here as the "One-Percent Initiative" because it would limit property tax rates to 1 percent of value, will not be on the ballot until November. The initiative, however, has become the primary candidates' favorite topic.

Vernon Ravenscroft, the best-known candidate in the GOP race, had been favored to win. But C.L. (Butch) Otter, the son-in-law of potato magnate J.R. Simplot, has parlayed his strong support of the One-Percent Initiative into growing strength in the polls.

Also making a pitch for the GOP gubernatorial nod is Larry Jackson, who won 124 games as a pitcher for three major league baseball teams.