WASHINGTON – Senate Democrats delivered the first of several promised election-year jobs bills Wednesday, passing a measure blending tax breaks for companies that hire unemployed workers with highway funding eagerly sought by the states.

The bipartisan 70-28 vote to pass the bill sends it to the House, where many Democrats say it is too puny — and where a revolt was brewing among lawmakers who said its allocation of highway money among the states is unfair. But pressure is on to pass it anyway to score a badly needed win for President Barack Obama and a Democratic Party that’s dropped badly in opinion polls.

Both Maine Sen. Susan Collins and Sen. Olympia Snowe voted to pass the bill.

A spokesman for House Speaker Nancy Pelosi, D-Calif., said the House was on track to pass the bill this week.

It’s the first major bill to pass the Senate since the Christmas Eve passage of a deeply controversial health care bill and the subsequent election of Massachusetts Republican Scott Brown,.

Democrats promise additional measures to create jobs, promising help for small businesses having trouble getting loans, aid for cash-strapped state governments, and subsidies for people who make their homes more energy efficient. But budget deficits are a worry, and future measures are going to be more difficult to pass — especially since a top Senate Democrat has blocked unused authority from the Wall Street bailout program from being used to ”pay for” jobs initiatives.

The bill contains two major provisions. First, it would exempt businesses hiring the unemployed from the 6.2 percent Social Security payroll tax through December and give them an additional $1,000 credit if new workers stay on the job a full year. The Social Security trust funds would be reimbursed for the lost revenue.

Second, it would extend highway and mass transit programs through the end of the year and pump $20 billion into them in time for the spring construction season. The money would make up for lower-than-expected gasoline tax revenues.

Some House Democrats complained that the Senate bill would unfairly favor states like California and Illinois at the expense of almost every other. But Pelosi spokesman Brendan Daly said lawmakers were working to resolve the issue.

”We are on a path to move forward this week,” Daly said in an e-mail.

The Senate’s $35 billion proposal — blending $15 billion in tax cuts and subsidies for infrastructure bonds issued by local governments with the $20 billion in transportation money — is a far smaller measure than last year’s $862 billion economic stimulus bill.

The measure cleared a key hurdle Monday when Brown and four other Republicans broke party ranks to defeat a filibuster. Republican leaders said Majority Leader Harry Reid, D-Nev., had used strong-arm tactics to bring the measure to the floor.

Brown took considerable heat from conservative commentators and bloggers for his Monday vote.