The so-called millionaire’s club added a few more members this year, with almost half of the Senate now claiming a net worth of more than $1 million.

At least 45 Senators — and eight possible presidential contenders — claimed wealth of at least that much on financial disclosure forms released Tuesday. That’s at least three more million-dollar Senators than the institution had when figures were released two years ago and five more than there were four years ago.

As recently as 1994, the Senate boasted only 28 Members with more than $1 million in net worth, a stunning increase by any measure.

As always, the disclosure forms allow a wide range for Senators to report the value of their assets. For its tabulations, Roll Call took the conservative route and used the lower number in the ranges listed on each form, meaning that the true worth of each Senator is probably quite a bit higher.

Many Senators, especially the more wealthy ones, have dozens or even hundreds of individual assets listed, meaning that the totals are likely off by hundreds of thousands of dollars — and in some cases, tens of millions. Sens. John Kerry (D-Mass.), Herb Kohl (D-Wis.), Hillary Rodham Clinton (D-N.Y.) and Jon Corzine (D-N.J.) are just a few examples of lawmakers whose actual net worth is likely much, much higher than what’s listed.

Senate Minority Whip Dick Durbin (D-Ill.) is one of the few Senators to list the exact value of his assets, and an analysis of his disclosure forms is indicative of how inaccurate the estimations can be.

If Durbin’s total wealth is tabulated using the more conservative method, he has about $550,000 in assets minus liabilities. But using the actual values he voluntarily supplied, his net worth tops out at a little more than $1 million — almost twice as much.

If, as seems likely, a dozen or more Senators fall into that category, the number of millionaires in the chamber could be closer to 60 or more.

Sen. Jim Bunning (R-Ky.) is one example. According to Roll Call’s tabulations, Bunning just missed the $1 million cut, coming in at just $3,000 shy. Unless all of his assets were valued at the lowest end of the ranges, the Kentucky Senator is certainly a millionaire.

North Dakota Sen. Kent Conrad (D) rang in at $941,000. His mortgage, listed as a liability, knocked him off the list, but there were dozens of asset listings in ranges large enough to virtually assure that he is also a millionaire.

Beyond just the inherent inaccuracy derived from the broad ranges into which Senators may categorize their assets, the disclosure forms are also noteworthy for what they don’t include at all. Not included on the financial disclosure forms are the values of Senator’s primary residences, vehicles, other personal property and their Senate pensions.

The case of Sen. Russ Feingold (D-Wis.) illustrates how much that excludes. Under the Roll Call’s formula for estimating a lawmaker’s assets (and subtracting liabilities, such as mortgages), Feingold listed only $6,000 in net worth on his forms.

Feingold’s office makes the rest of his assets public, however. When he includes his $177,000 pension (which includes his pension as a state Senator), along with the current market value of his home ($260,000) and other sundry items and subtracts the actual amount of his liabilities, his total jumps to $257,000.

Despite this boost, Feingold is one of only three of the 11 frequently mentioned 2008 presidential hopefuls in the Senate to not make the $1 million list.

Sens. Joseph Biden (D-Del.) and Rick Santorum (R-Pa.) are the others. Santorum has less than $100,000 in assets minus liabilities, according to Roll Call’s tabulations. Biden, by contrast, is for all intents and purposes a millionaire. Using conservative estimates, his net worth is somewhere above $900,000.

In descending order by wealth, the following are other possible presidential candidates who make the millionaire’s cut: Kerry, $170.1 million; Senate Majority Leader Bill Frist (R-Tenn.), $14.2 million; Clinton, $13.5 million; Sens. John McCain (R-Ariz.), $12 million; Sam Brownback (R-Kan.), $2.3 million; Chuck Hagel (R-Neb.), $2.3 million; Evan Bayh (D-Ind.), $1.3 million; and George Allen (R-Va.), $1.1 million.

To be sure, some Senators married extremely well or have spouses equally as wealthy as they. Teresa Heinz Kerry, the heir to the ketchup fortune, obviously comes to mind, but Kerry is not the only one to benefit on paper from his or her wealthy spouse. The financial disclosure forms list the assets of Members’ dependent children and spouses, and this often accounts for a large part of the reported wealth.

But much of the spouse’s assets and incomes are also vastly underreported. Members don’t have to itemize spousal incomes over $1,000, so former President Bill Clinton’s rumored multimillion dollar book deal is only listed as “over $1,000” on his wife’s disclosure form.

What’s impressive about the Senate’s tally of at least 45 millionaires this year is how that number managed to grow even as the chamber lost a handful of millionaires to retirement at the beginning of this Congress. Ex-Sens. Peter Fitzgerald (R-Ill.), John Edwards (D-N.C.), Ben Nighthorse Campbell (R-Colo.) and Bob Graham (D-Fla.) — millionaires all — left the list this year.

Who joined? Freshman Sens. Johnny Isakson (R-Ga.), Mel Martinez (R-Fla.) and Tom Coburn (R-Okla.) all were newcomers to the millionaires club. But the list also expanded with nonfreshmen. Sens. Jeff Bingaman (R-Ala.), Tom Harkin (D-Iowa), Daniel Inouye (D-Hawaii), Evan Bayh (D-Ind.), Allen and Durbin, all saw their assets jump over the million dollar mark for the first time.

Jared Allen, Teddy Davis and Matthew Murray contributed to this report.