Rumor has it that Detroit's Mayor Jerome P. Cavanagh, has been number one on President Johnson's list of possible Secretaries of the New Housing and Urban Affairs Department. Cavanagh, as one of the outstanding mayors in the nation, is an obvious choice for the new Cabinet post. At the same time, the Mayor has such a strong and promising political base in Detroit that he probably doesn't want a merely appointive job.

Cavanagh's strength at home can be measured by the size of his re-election victory last month. Although his opponent tried to ignite casual bigots' fear of "crime in the streets," he only got 144,000 votes to the Mayor's 295,000. Like most liberals Cavanagh could count on the County AFL-CIO and all the major Negro organizations for support, but he also received votes, money, and testimonials from automobile executives and most local businessmen.

The breadth of Cavanagh's support is clearly a result of his spectacular record in office. After his upset victory four years ago over incumbent Louis Miriani, Cavanagh did not owe any political favors and was able to frame both definitions and solutions of the city's problems. He began by slapping an income tax on everyone who lived or worked in the city, and in four years the city has been able to turn a large deficit into a surplus, to increase municipal services, raise salaries (police salaries went up 25 per cent), and lower the property tax, Cavanagh's police commissioners reformed the Police Department, and his bright young department heads have consistently been first in line for antipoverty funds and other types of federal aid.

Cavanagh's popularity and his strength lead to only one conclusion: that he wishes to seek higher office in Michigan. He is probably more interested in the Senate than in the Governorship, but both of the state's seats are held by Democrats. (Detroit municipal officers are nonpartisan, but Cavanagh is known to be a Democrat.) Senator Philip Hart, who is 51 and was reelected last year by 900,000 votes, is not about to retire, but the other seat, held by 70-year-old Pat McNamara might be up for grabs in 1966.

Twelve years ago McNamara was president of a pipe-fitters' local and a member of the Detroit Board of Education. Today he is chairman of the Senate Public Works Committee and the Joint Congressional Committee on the Aging and number two man on Labor and Public Welfare. He has become, in other words, a powerful man, contrary to his and everyone else's expectations, and he probably wants to remain powerful for the rest of his life. How long that will be no one can say; McNamara has been in bad health for years and is just stubborn enough to go on that way for another term or two. At any rate, he has announced several times that he will definitely be running for reelection.

In case he doesn't, the first man in line for the job is six-term Governor G. Mennen (Soapy) Williams. Williams has been an assistant Secretary of State for an unusually long time, and he has been spending a lot of time in Michigan lately, doing things like buying a new house in Grosse Pointe and introducing the Supremes at the State Fair. Williams is still popular enough to win a Democratic primary and almost any statewide election without difficulty. If he is not able to run for the Senate, he might choose the race against Republican Governor George Romney. Romney will certainly not run for Senator; a man who believes so devoutly in his own infallibility could never stand being number 99, even in the United States Senate.

Only if Williams does not run for Governor will Cavanagh have an open avenue. But in the middle of the avenue will be standing lion-like George Romney, his graying temples glinting in the sunlight. Romney will be a tough opponent, but not as unbeatable as metaphor and newsmagazine suggest.

Romney never demonstrated real vote-getting power with Michigan voters until he beat long-time Democratic State Chairman Neil Staebler by 380,000 votes last year, in the face of the Johnson landslide. But in 1964 a unique combination of factors--pervasive prosperity, a horror of Barry Goldwater, the recent death of President Kennedy--led people in most states to vote incumbents, of either party, in unprecedented proportions. Voters with little party identification or interest in politics, voters who form the pivotal "undecided" segment of the electorate, swung almost unanimously to incumbents.

It was just these "undecided" voters who gave George Romney his extraordinary margin. The usually accurate Detroit News poll taken just before the 1964 election gave Romney 48 per cent, Staebler 44, with the rest undecided. The final result was Romney 56, Staebler 44. Romney must have received something like 95 per cent of the undecided vote.

These figures suggest that Romney has the solid support of a large part of the Michigan electorate--but not quite a majority. The voters who gave him his big 1964 margin were those with the weakest and most changeable preferences, and they were motivated in large part by transient factors--most notably their reaction to the assassination of President Kennedy. If this critical portion of the Romney majority is so soft, then it is just possible that he can be beaten when he runs for reelection (to a newly-lengthened four-year term) next year.

That is where Mayor Cavanagh comes in. If Williams has the affection of the Michigan Democratic rank and file, Cavanagh probably has more strength with the weakly motivated center of the electorate. A disproportionate number of such voters are young, and for them the 37-year-old Cavanagh has great appeal. They associate him with his record as mayor, while they tend to identify Williams with the 1958 recession and the hatchet job he took from the Republican legislature and newspapers.

If Cavanagh is to get through to these weakly affiliated voters, he must convince them that he can do what Romney has been largely unsuccessful at: breaking the deadlocks that have tied up Michigan politics since the 1940's. Michigan governors, for example, have been talking about reforming the state's regressive tax structure for eight years.

Cavanagh has the advantage of being a member of the majority party and, at the same time, a non-partisan official free from association with those who have been mired in partisan conflict for years. He also has the advantage of having one of the most astute political brains around; if he decides to run, his decision will be sign enough that he has a solid chance to win.