WASHINGTON — The Republican Party placed $700,000 in television ads in Ohio on Tuesday, a scaled-back ad campaign amid growing doubts by party officials that GOP Sen. Mike DeWine can win re-election in the battleground state.

The ads by the party are smaller than recent million-dollar ad buys by the National Republican Senatorial Committee. But party officials touted the ads as evidence that they were not abandoning the state or giving up on DeWine.

Strategists from both parties were following the Republican steps closely because the GOP had chosen Ohio, Tennessee and Missouri as political fortifications against a Democratic takeover of the Senate. Democrats need a net gain of six seats to win control of the Senate.

Polls this week in Ohio show DeWine trailing his Democratic opponent, Rep. Sherrod Brown, by 7 to 12 percentage points.

Republican Party officials are turning their sights to Virginia to offer needed help to Sen. George Allen, who has been unable to stop a rapidly tightening race with Democrat Jim Webb. Virginia already is part of the party’s aggressive voter turnout operation and party officials are said to be weighing a substantial ad campaign in the state as well. The Democratic Senatorial Campaign Committee already is spending about $1.1 million on ads in Virginia against Allen.

Allen, once considered a likely candidate for the Republican presidential nomination in 2008, holds a financial advantage in the campaign but has lost ground to Webb after a series of campaign mishaps. A recent Washington Post poll had Allen and Webb virtually tied, with Allen’s lead within the poll’s margin of error.

In New Jersey, the Democrats on Tuesday countered a Republican ad purchase in a race for a potentially vulnerable Democratic-held Senate seat. Democratic Sen. Robert Menendez is facing a strong challenge from Republican Tom Kean Jr., son of a former New Jersey governor.

Republicans spent $500,000 this week to air ads in New Jersey against Menendez. The Democratic Senatorial Campaign Committee began airing an ad Tuesday evening against Kean, linking him to Bush’s Iraq war policy. New Jersey is served by television stations in New York and Philadelphia, making it one of the most expensive media markets in the country. The Democratic and Republican ads are airing in New York only.

Sen. Charles Schumer of New York, the chairman of the Democratic Senatorial Campaign Committee, conceded Tuesday that New Jersey is the only Democratic-held seat where Democrats do not hold comfortable double-digit leads, but said the party can withstand a last-minute expenditure against a Democratic senator.

“We believe we have the ability on defense should they put a lot of money in one state, particularly a blue state, to answer it,” he said.

Republicans were also taking a second look at some House races they once considered safe from Democrats.

In two new battlegrounds, Republicans began airing television ads in races in Pennsylvania and Minnesota that were not previously considered competitive. The National Republican Congressional Committee reported it would spend $100,398 to help GOP Rep. Gil Gutknecht’s re-election race in Minnesota against Democratic challenger, Tim Walz. Democrats signaled they would begin airing ads in that rural Midwest district as well.

The Republicans also began airing an ad against Democrat Jason Altmire, who is seeking to unseat Republican Rep. Melissa Hart.

The NRCC also is paying for polling in the Kentucky congressional district of Rep. Anne Northup. Such polls usually are commissioned to determine whether the party needs to put in resources to help a candidate in trouble.

Republican officials also appeared to have decided not to use more than $1.5 million in television time initially reserved to advertise against eight-term Democratic Rep. Chet Edwards of Texas. Two television station managers in the Waco area and the Edwards campaign said Tuesday that the NRCC was not planning to spend the money in Edwards’ race against Republican Van Taylor.

But Republicans reported spending money on television ads in the Texas congressional contest to replace former House Majority Leader Tom DeLay. The race pits former Democratic Rep. Nick Lampson against a Republican write-in candidate, Shelley Sekula-Gibbs. The contest has been considered an easy pickup for Democrats.

Both parties have also stepped up their spending on other means of reaching voters, particularly direct mail and automated phone calls. Since Friday, the National Republican Congressional Committee has about $350,000 in mailings and phone banks, most critical of Democratic candidates. The Democratic Congressional Campaign Committee reported more than $550,000 spent on phone banks, mostly against Republican candidates.

The NRCC also reported airing about $2 million in television commercials in nine highly competitive congressional districts. Republicans have hope they can hold onto the seat of former Rep. Mark Foley, who resigned in the midst of a scandal over sexually explicit electronic messages to teenage male pages. The NRCC reported spending more than $270,000 on an ad opposing the Democratic candidate for the seat, Tim Mahoney.