If ever there were a moment for Democrats to press their political advantage, this is it. Their message on many of the biggest national issues — taxes, guns, education spending, financial regulation — has widespread support, and they have increased their numbers in both houses of Congress. But after years of being out-yelled by strident right-wing ideologues, too many in the Democratic Party still have a case of nerves, afraid of bold action and forthright principles.

That’s particularly evident in the Senate, which the party controls. Last week, Democrats had a rare opportunity to change the Senate’s rules by majority vote and reduce the routine abuse of the filibuster by Republicans, which has allowed a minority to slow progress to a crawl. But there weren’t enough Democrats to support real reform, so a disappointing half-measure was approved. The reason was fear: Fear that they might return to the minority one day, fear that a weakened filibuster might hurt them, fear that Republicans might change the rules to the disadvantage of Democrats if they regain a majority.

Similarly, fear is preventing many Democrats from fully embracing President Obama’s sensible and long-overdue proposals on curbing gun violence. A proposal to require background checks on all gun buyers — the top priority of most gun-control groups because of its effect on handgun proliferation — is beginning to win strong bipartisan support. But Democrats from swing states — including Harry Reid of Nevada, the majority leader — are backing away from a bill to ban semiautomatic assault weapons, and it is not clear if the Senate will vote to prohibit high-capacity ammunition magazines.

Senate Democrats are not even united on the obvious need to raise additional tax revenues as part of budget agreements to reduce the deficit. Though Senator Charles Schumer of New York is pushing to raise more revenue through tax reform, Max Baucus of Montana, who leads the tax-writing Finance Committee, has resisted the idea.