Washington (CNN) -- Unlike most issues these days that divide along party lines, the immediate fate of President Obama's new gun proposals will depend not as much on Republicans as his fellow Democrats in the Senate.
Senate Democratic leadership sources tell CNN that passing any new legislation will be extremely difficult because more than a dozen vulnerable Democrats from conservative states will probably resist much of what the president is pushing.
These Democratic sources say the most likely legislation to pass will be strengthening background checks, since it is the least overt form of gun control and it also appeals to gun rights advocates' emphasis on keeping guns away from people with mental health and criminal problems.
Although Senate Democrats like Dianne Feinstein will still make a high-profile push to renew the assault weapons ban and limit ammunition magazines to 10 rounds, senior Democratic sources say it is hard to see those measures getting enough support to pass the Democratic-led Senate.
The focus is on the Senate because Senate Democratic leaders know that House Republicans will not act on anything until the Senate does.
Democratic leadership sources say they intend to spend next week -- the first week the Senate is in session -- canvassing red-state Democrats to see what, if anything, is doable. Democratic senators who advocate various gun control measures will be lobbying their colleagues as well.
At a certain point, Democratic leaders will decide the best course of action, if any. Democratic leadership sources emphasize what Senate Majority Leader Harry Reid said in a PBS interview in recent days: They will not vote on any legislation unless they have 60 votes, enough to break a filibuster.
Democratic leadership sources say they have no intention of putting their members in a politically vulnerable position on a gun measure unless they are sure it can reach the president's desk.
In the short term, that would mean not only getting red-state Democrats on board, but at least a handful of Senate Republicans as well.
There is some hope that Democrats may be able to persuade GOP Sen. Mark Kirk of Illinois, a moderate, to help shape bipartisan legislation that can pass.