Conservative and liberal groups are only beginning their battle over the Supreme Court vacancy, with a smattering of television ads and behind-the-scenes research serving as warning shots in what's sure to be an expensive fight that will color November's elections.

Activity will only ramp up once President Barack Obama names someone to replace the late Justice Antonin Scalia — a nomination Senate Majority Leader Mitch McConnell, R-Ky., and other Republicans promise the chamber will never consider. Many expect Obama to announce his pick next week.

With the court's 4-4 balance between liberal and conservative justices in play, both parties and their allies are reaching out to rally their memberships, solicit contributions and savage the opposition.

The conservative Judicial Crisis Network has run TV spots backing GOP senators in seven states and digital ads targeting Democrats in four others, while its leader wrote an article criticizing one potential nominee for a case she handled as a public defender a decade ago. On its website, the legislative arm of the National Rifle Association links readers to an article titled "Justice Barack Obama?" suggesting that scenario should Democrat Hillary Clinton become president.

The Senate Majority PAC, backing Democrats, has launched a New Hampshire TV ad accusing GOP Sen. Kelly Ayotte, in a competitive re-election race, of "ignoring the Constitution, not doing her job." And Citizens United, dedicated to overturning the Supreme Court decision that unleashed unlimited campaign spending by corporations and unions, has aired commercials pressing Ayotte and Sen. Roy Blunt, R-Mo., to consider a nominee. A group of 21 Democratic attorneys general penned a letter warning Senate leaders not to "undermine the rule of law." MoveOn.org and other progressive groups plan rallies outside senators' home-state offices on a March 21 "National Day of Action."

"A Supreme Court nomination is the No. 1 top priority for almost any conservative group," said Carrie Severino, the Crisis Network's policy director, a sentiment shared by liberals, too. "Almost every issue ultimately finds its way to the Supreme Court."

Democrats and liberals have focused on Senate Judiciary Committee Chairman Charles Grassley, R-Iowa, and other Republican senators seeking re-election this fall in swing states like Ohio, Pennsylvania and Wisconsin. Backed by nearly all GOP senators, Grassley has said his panel won't hold a hearing on Obama's choice.