Senate candidates in November's election raised a record $145.8 million, a 26 percent increase from 1982, Common Cause reported yesterday.

A study by the self-styled citizens lobby showed that spending by the 65 Senate candidates in the general election was $136.9 million, 21 percent more than two years earlier.

This means that the candidates took in $8.9 million more than they spent in the two-year election cycle, but the actual surplus was less, principally because Common Cause did not include loan repayments in its campaign spending totals. The candidates still wound up on Dec. 31 with $7.3 million in cash on hand, 55 percent more than the amount left over in 1982.

Under federal election spending laws, the candidates can use the unspent money for "any lawful purpose," from defraying Senate office expenses to giving the money to charity to building a war chest for the next campaign. Under a special "grandfather" clause that Congress gave itself in 1979, lawmakers in office as of Jan. 8, 1980, can convert the money for personal use.

The Common Cause study also showed that political action committee contributions to Senate candidates amounted to $27.9 million, an increase of 28 percent from 1982.

"A look at the campaign finance reports for Senate candidates in 1984 is a signal to everyone planning to run in 1986 that they had better be prepared to raise massive amounts of money," Common Cause President Fred Wertheimer said in a statement accompanying the report. "This system has lost all resemblance to the democratic ideal that any qualified citizen could run for a seat in the United States Senate."

Preliminary figures compiled by the Federal Election Commission for all 255 candidates who entered 1984 Senate contests show total spending of $170 million.

The North Carolina race between Sen. Jesse Helms (R) and then-Gov. James B. Hunt (D) produced a high-water mark. Helms raised $16.5 million and Hunt slightly more than $10 million; of that, Helms spent $16.2 million, and Hunt $9.2 million, making the contest by far the most expensive Senate race ever.

The 1984 Texas Senate race was runner-up in that category. The winner, Phil Gramm (R), spent $9.4 million, while Lloyd Doggett (D) paid out $5.5 million.

Next was West Virginia, where John D. (Jay) Rockefeller IV (D) raised and spent more than $12 million in moving from the governor's mansion to Capitol Hill.

In all, Common Cause said, 11 candidates (eight of them victorious) spent more than $3 million in the 1983-84 period. Four of them -- Helms, Rockefeller, Gramm and Hunt -- broke the record of $7.5 million set by Helms in 1978.

The biggest surplus was compiled by Sen. J. Bennett Johnston (D-La.), who had $984,831 cash on hand. Sen. Sam Nunn (D-Ga.) had the next biggest cushion, with $676,199 left after an easy reelection campaign.