President Obama's gun-control package was always going to be a tough sell in the Republican-led House -- but the plan is already running into resistance, or at least hesitation, from moderate Democrats in the Senate. 

The lukewarm response in the Senate to Obama's highly anticipated anti-gun violence plan portends an uphill climb for the legislation. And it underscores how, as the president's backers prepare to launch a veritable campaign to promote the plan, they will be pressuring members of their own party as much as reluctant Republicans.