I was not at all surprised when Andrews recently announced that he would challenge Sen. Frank Lautenberg (D-N.J.) this year. Although Andrews’ announcement was not expected, and I had no early knowledge of it, the Democratic Congressman has already run statewide once and has made no secret over the years of his desire to seek higher office.

The immediate reaction inside the Beltway was predictable: Had Andrews lost his mind, challenging an incumbent member of his own party?

Andrews’ six Garden State House Democratic colleagues immediately fired off a letter to him asserting that he “has failed to gain the necessary support to realistically compete in this race” and demanding that he drop his Senate bid.

Is Andrews crazy to take on Lautenberg? And why on earth would the state’s Democratic House Members sound so hysterical in denouncing what they see as a Don Quixote-like effort?

Andrews, who certainly was one of the brightest students at Bucknell when I was on the faculty, acknowledges that he is an underdog in the race. And he is.

Lautenberg, 84, is serving his fourth (nonconsecutive) term, is personally wealthy (though hesitant to spend his own money) and is running in a state squeezed between the expensive New York City and Philadelphia media markets. He has the support of the Democratic Senatorial Campaign Committee and showed $4.3 million in the bank at the end of December.

Andrews, on the other hand, had just less than $2.4 million in the bank at the end of last year, represents a South Jersey Congressional district and is not widely known in the important northern third of the state. He lost his only statewide bid, for governor, in the 1997 Democratic primary by a nose.

A Benenson Strategy Group poll from early April for the DSCC found Lautenberg’s job approval among Democrats at 76 percent, while 57 percent said they would vote to re-elect him and only 12 percent said they would not. In the ballot test, Lautenberg led 52 percent to 21 percent.

“Andrews looks to have no clear path to victory,” the polling memo says.

Here’s why Lautenberg should be concerned: Andrews is smart and analytical, and he wouldn’t have jumped into the race without looking at every angle six ways to Sunday. He’s not a flake and not an ideologue on a mission. He’s not Dennis Kucinich or Mike Gravel.

And I’m certainly not the only one who thinks that Andrews shouldn’t be dismissed by Lautenberg or his supporters. One veteran Democratic insider with whom I talked recently thinks the Senator has a real fight on his hands, even though he should win: “The primary will be competitive. But it will be hard for Andrews. Still, it’s not as if Rob is just a long shot.”

Geography is on Lautenberg’s side, since Andrews is frequently identified as a South Jersey candidate and most of the Democratic primary votes are up north. Lautenberg has the party’s endorsements in 14 counties (to Andrews’ seven), including Union, Bergen and Middlesex.

But the challenger has picked up a handful of key endorsements in Northern and Central New Jersey, including influential state Sen. Ray Lesniak of Union County, Middlesex County state Sen. Barbara Buono, Essex County Democratic power broker Steve Adubato and Hudson County state Sen. Sandra Cunningham.

Andrews’ supporters argue that while Lautenberg has “the party line” in populous northern counties, local party leaders are more concerned with local and state offices, not with a federal office. And they add that some important Democratic officeholders in those counties are backing Andrews.

Lautenberg also must be concerned about turnout, which could be microscopic in June. Garden State voters already voted in the state’s presidential primary, and with few other races on the ballot in June, most Democrats won’t bother to cast a vote in the Senate primary.

A low statewide turnout should help Andrews, because it could exaggerate the importance of South Jersey voters, who are certain to be more provincial about their choice, and of voters who want “change.”

Lautenberg is trying to portray Andrews as more hawkish on Iraq and noticeably more conservative. Andrews generally minimizes the ideological differences between the two candidates, preferring to rest his bid on generational politics.

Ultimately, the primary could come down to personality, style and age. “Frank doesn’t engender a lot of real loyalty. He’s not a nice guy,” one observer said. But Andrews, while savvy and astute, isn’t regarded as terribly warm, either. At 50, Andrews is much younger than Lautenberg.

The short campaign (the primary is June 3) could help Lautenberg, since it means less time for him to make a mistake. But party boss George Norcross, a major figure throughout Andrews’ career and the Congressman’s top strategist, has had success in the past with last-minute surprises.

Given the competitiveness of the primary, why did Andrews’ House colleagues line up so quickly behind Lautenberg and scream for Andrews to drop his Senate bid? The answer is simple, says former Democratic state party Executive Director Tom O’Neil, a thoughtful observer of state politics. “They all want what he wants: a Senate seat. So they don’t want him to get Lautenberg’s. If he wins it, there won’t be another open Senate seat for two decades.”

Lautenberg starts as the favorite. But don’t kid yourself: Andrews is for real, and this is a primary worth watching.

Stuart Rothenberg is editor of The Rothenberg Political Report.