A Harbinger of Slippage? A new NBC-Associated Press poll contains the first hint that one of President Reagan's main political attributes, the perception of him as a strong leader who is able to control the economy, is beginning to erode. In the poll, 43 percent of those interviewed say they feel that no president "can reduce inflation."

Both as a campaigner and as president, Reagan successfully conveyed the impression that he is a strong leader who can handle the nation's economic problems. He contrasted himself to former president Jimmy Carter, who maintained that the policies of the oil-producing nations, about which he could do little, were the principal cause of inflation. Reagan said the policies of the U.S. government, which he would change, were the leading cause of inflation.

The distinction was not lost on voters. The NBC-AP question, however, suggests that they may think Reagan doesn't have control, and is one that public opinion experts will watch in the months ahead.

For Liberals the Times Are Lookin' Lean: The annual rating of the liberal Americans for Democratic Action shows that the Senate took a sharp swing to the right in 1981, primarily because of the freshmen elected in 1980. Of the 18 newcomers, 16 of whom are Republicans, 14 got a liberal rating of 25 percent or less. The liberal rating of the Senate as a whole dropped from 46 percent in 1980 to 40 percent in 1981, based on such key votes as Reagan's proposed cutback of minimum Social Security payments and youth training, funding of the B1 bomber, military aid to Chile and sale of airborne warning and control system (AWACS) aircraft to Saudi Arabia.

Democratic Sens. Edward M. Kennedy and Carl Levin got 100 percent ratings from the ADA, while Dale Bumpers, Gary Hart, Patrick J. Leahy, Claiborne Pell, Paul S. Sarbanes and Paul E. Tsongas received 95 percent ratings. Eight Republicans--Strom Thurmond, Barry Goldwater, Jesse Helms, John P. East, Jake Garn, Orrin G. Hatch and Steve Symms--got zero ratings. The highest Republican score, 55 percent, was registered by Lowell P. Weicker Jr. and Mark O. Hatfield; the lowest Democratic rating of 15 percent was scored by John C. Stennis.

Familiar Names, If Not Familiar Faces: Former House minority leader John J. Rhodes of Arizona announced that he is retiring after 30 years in the House after praying for the wisdom to know when to quit. Among the Republicans considering a run for his seat are Rhodes' son, Jay, a Phoenix area lawyer, and Dave Udall, a Mesa lawyer and a distant cousin of Rep. Morris K. Udall (D-Ariz.).

Another Entrant: As expected, Salt Lake City Mayor Ted Wilson (D) announced his candidacy for the U.S. Senate seat held by Republican Orrin G. Hatch, buoyed by the latest Salt Lake Tribune poll, which shows Hatch holding a slim lead. Hatch is the choice of 51 percent of Utah voters, Wilson the choice of 40 percent. The small number of undecideds indicate that both have high name identification, and the poll shows that the swing voters are the independents, who are almost evenly divided.

Politics Makes Strange, Uh, Running Mates: Lots of married couples are business or professional partners and in that spirit Genevieve Marcus and Robert Smith of Los Angeles formally announced their desire to be partners, in the leadership of California. She is running for the Democratic gubernatorial nomination and he is running for the Democratic nomination for lieutenant governor. If elected, they promised they will move into the same offices and share their powers, the first his-and-hers statehouse.

Smith said he trusted his wife "implicitly" to share her powers, noting that "we rotate power in our family." This prompted one reporter to inquire if the voters might not worry about a gubernatorial divorce and court fight over who gets custody of California.

Maybe They'll Put It on the License Plates: Alabama Gov. Fob James' first-of-a-kind "Address to the People of Alabama," scheduled to be mailed with state income tax forms, may confuse some voters. The report is straightforward enough on how the taxpayers' money is being spent. But state convicts who have spent the past weeks stapling it to the tax forms also thoughtfully added to James' picture. Some show him with a mustache penciled in, some with a beard.