Story highlights Public support for new gun measures has fallen dramatically since Newtown massacre

Support spiked after elementary school shootings but has dropped by double digits since

Largest drop in support was among older Americans and those who live in rural areas

Is the clock ticking on gun control?

While support for many gun control policies remains high in the wake of the horrific shootings at Sandy Hook Elementary School in Connecticut, polls conducted over the past few weeks suggest that three-and-a-half months after the tragedy, public backing for major new gun laws overall appears to have dropped significantly.

A CBS News survey released earlier this week indicated a 10-point drop in the public backing of stricter gun laws, from 57% immediately after the shootings in Newtown, Connecticut , in December when a heavily armed gunman killed 20 young students and six adults, to 47% now.

That poll was in line with a CNN/ORC International survey released last week that indicated a nine-point drop in the percentage of Americans who favor major restrictions on guns or an outright ban on gun ownership, from 52% following the shootings to 43%.

Other polls have shown changes within their sampling error but in the same downward direction.

An ABC News/Washington Post poll released in mid-March showed support for stricter gun laws moving from 54% to 52%. That two-point margin was within the survey's sampling error.

And a Fox News poll released last week indicated majority backing -- but some slippage -- in support for specific proposals like banning assault rifles and semi-automatic weapons and high-capacity ammunition clips.

JUST WATCHED Why U.S. can't come together on gun laws Replay More Videos ... MUST WATCH Why U.S. can't come together on gun laws 07:50

JUST WATCHED Filibuster on the horizon Replay More Videos ... MUST WATCH Filibuster on the horizon 03:30

JUST WATCHED Hickenlooper: Gun control 'a tough sell' Replay More Videos ... MUST WATCH Hickenlooper: Gun control 'a tough sell' 02:01

"Opinion on gun control was fairly steady over the past few years, but seemed to spike after the Connecticut shootings," CNN Polling Director Keating Holland said. "The big question is whether support for major new gun laws has simply dropped back down to that previous level or whether the slide will continue even further."

So what's causing the drop in support? The surveys, including CNN's, offer clues.

"Support for stricter gun control has fallen dramatically among two groups -- older Americans and people who live in rural areas," Holland said. "In the immediate aftermath of the shootings in Connecticut, the number of rural Americans who supported major gun restrictions rose to 49% but now that support has dropped 22 points. Support for stricter gun laws dropped 16 points among Americans over 50 years old in that same time."

The new polls suggest that federal lawmakers pushing for gun control might have waited too long to act.

Senate Majority Leader Harry Reid announced late last week that he would move ahead on a bill that would expand background checks for gun sales and stiffen gun trafficking penalties when the Senate returns from the two-week recess it's currently taking. While national polling indicates extremely strong support for background checks, Reid's bill could face a very tough go of it in Democrat-controlled Senate, let alone the GOP-dominated House.