Democrats have seized a major early advantage in their campaign to retain control of the Senate by recruiting at least 10 current and former statewide elected officials for this fall's elections -- a far heavier roster of big-name challengers than the Republicans have assembled.

With candidates ranging from former governors Charles S. Robb in Virginia and Bob Kerrey in Nebraska to Gov. Richard H. Bryan in Nevada, the Democrats have taken the offensive in the GOP's backyard, even though they are defending more seats than the Republicans.

Under the current, still incomplete, lineup of candidates, the number of Republican-held seats that appear seriously threatened by Democrats is nearly twice the number of Democratic seats under heavy assault from Republicans.

Also, among the 33 seats at stake in the elections, Democrats appear to have considerably more "safe" seats than the Republicans, with Virginia and Maryland considered securely in the Democratic column -- a first for Virginia in two decades.

The "stature gap," as Democratic Senatorial Campaign Committee Chairman John F. Kerry (D-Mass.) calls it, contributes to a widely held assumption that Democrats start the campaign year with odds favoring them to retain control of the Senate and perhaps even increase their current 54-to-46 margin.

Other factors may become more important as the November elections approach -- the status of the presidential race, the economy and world tensions -- and both sides expect the current gap in many races to close as the more obscure challengers become better known. Republicans make the point that some of their lesser-known candidates have the potential for strong finishes in a relatively large number of states where polls show Democratic incumbents to be vulnerable.

They note that several Republican House members are mounting strong challenges for Democratic-held seats, including House Minority Whip Trent Lott, running for the seat being vacated by retiring Sen. John C. Stennis (D-Miss.).

Moreover, they say they anticipate serious bids by such non-officeholders as former Army general and football hero Peter M. Dawkins against Sen. Frank R. Lautenberg (D-N.J.), well-known farm broadcaster Conrad Burns against Sen. John Melcher (D-Mont.), and State Senate GOP leader Susan Engeleiter among several Republicans vying for the seat of retiring Sen. William Proxmire (D-Wis.). Cleveland Mayor George Voinovich starts with a strong local base to challenge Sen. Howard M. Metzenbaum (D-Ohio).

But Republicans concede disappointment in their failure to recruit big GOP names that could have tipped the odds in a half-dozen or more states, where potentially vulnerable Democratic senators may be able to coast to reelection in the absence of a serious Republican challenge.

Within the last few weeks, Manhattan's U.S. Attorney Rudolph W. Giuliani decided against an election effort and former Tennessee governor Lamar Alexander opted to become president of the University of Tennessee, substantially easing the reelection fears of Sens. Daniel Patrick Moynihan (D-N.Y.) and James R. Sasser (D-Tenn.).

"We didn't get some of our top people in all the races, but it wasn't for the lack of trying . . . and they {the Democrats} still have more vulnerable people than we have," said Sen. Rudy Boschwitz (R-Minn.), chairman of the National Republican Senatorial Committee.

While Republicans argue it is too early to draw any broader significance from the lopsided lineup of big-name candidates, Democratic campaign committee chairman Kerry suggests it may be a "harbinger of a swing" toward the Democrats and their priorities.

In all, the Democrats have recruited five current and former governors, two lieutenant governors, two attorneys general and one secretary of state, along with five House members. The Republicans have lined up about the same number of House members but can claim few proven statewide vote-getters among their certain or likely challengers. The most prominent of these, former senator Slade Gorton (R-Wash.), who was defeated for reelection in 1986 after one term, and former Wisconsin governor Lee Dreyfuss, who served one term in the 1970s, have not said yet whether they will run.

Moreover, some of the GOP's strongest figures are likely to be pitted against equally strong, or stronger, Democratic aspirants. For instance, Republicans' high hopes that Rep. Connie Mack (R-Fla.) could exploit the surprise retirement of Sen. Lawton Chiles (D-Fla.) dimmed a bit when former Democratic governor Reubin Askew jumped into the race. In Mississippi, Lott faces tough Democratic opposition from either Rep. Wayne Dowdy or Secretary of State Dick Molpus, party moderates who face each other in the "Super Tuesday" primary March 8.

Conversely, some of the Democrats' gubernatorial heavyweights are targeted against some of the GOP's more vulnerable incumbents, such as in Bryan's race against Sen. Chic Hecht in Nevada. In Nebraska, Kerrey will take on the survivor of a divisive primary fight in May between recently appointed Sen. David Karnes (R) and Rep. Hal Daub (R).

While Republicans are trailing in the race for big names, their opportunities have been broadened by the relatively large number of retirements, three from each party. Although they are considered virtually certain to lose one seat (Virginia), they are equally assured of electing Rep. James M. Jeffords (R) to the seat now held by Sen. Robert T. Stafford (R-Vt.) and are at least competitive in Florida, Mississippi, Washington and Wisconsin.