Kevin Johnson, and Erin Kelly

USA TODAY

WASHINGTON — New questions about the ultimate goal and the extent of Russia's intrusions into U.S. political institutions continued to emerge Monday after intelligence officials briefed lawmakers last week with the dramatic assessment that Russian hackers sought to tilt last month's general election to President-elect Donald Trump.

Trump has dismissed the conclusions outright, and the FBI has suggested that the assessment — while possibly accurate — so far lacks definitive evidence necessary, said two U.S. officials who are not authorized to comment publicly.

The questions over hacking have thrust Russia, which long loomed as a potential threat to the integrity of the general election, back into center of U.S. national security concerns, as Trump assembles key appointees for his administration, including the pending announcement on his choice for secretary of State.

Yes, Donald Trump, you can catch hackers not in the act

A review of how the issue escalated, with Russia now suspected of attempting to sway the election in Trump's favor and what happens next:

Q: How did last week's intelligence assessment differ from previous reports about Russia's hacking of U.S. political institutions?

A: In October, U.S. officials formally identified the Russian government as the source of intrusions into Democratic Party systems. Those hacks— which produced a trove of embarrassing internal communications for public distribution on the websites DCLeaks and WikiLeaks — led to the resignation of Democratic National Committee Chairwoman Debbie Wasserman Schultz on the eve of the national convention. The leaks also led supporters of Sen. Bernie Sanders to loudly protest that the Democratic primaries were rigged against him.

The October finding, announced by Director of National Intelligence James Clapper and Homeland Security Secretary Jeh Johnson, concluded that the disclosures were "intended to interfere with the U.S. election process.'' The new assessment takes it a major step further, indicating that Russia aimed to sway the election in Trump's favor. The conclusion is that Republican Party computer systems also may have been breached, but that internal information was not distributed publicly. The Republican Party denies that its computers were hacked.

Yes, 17 intelligence agencies really did say Russia was behind hacking

Q: On what points of the new Russian assessment do the CIA and other intelligence authorities differ with the FBI?

A: The FBI does not dispute that the CIA's assessment could be accurate, said a U.S. official with knowledge of the matter. The difference lies in the institutional standards the agencies require in reaching such conclusions. While the CIA develops assessments based on a broad interpretation of available data, the FBI, as a law enforcement agency, requires a standard of proof that could sustain a possible criminal prosecution.

There have been differences, the official said, in how much weight to ascribe a range of possible motives: Were the Russians specifically seeking to tilt the election in favor of Trump? Was the effort designed to damage Democratic nominee Hillary Clinton's future ability to govern, believing that she was destined to win? Or was the operation a hedging of bets to sow confusion and undermine confidence in the process?

Of the assessment that the Republican Party systems were likely breached, the official said the picture is not entirely clear. While not dismissing the intelligence community's conclusion, the official said a more definitive determination has not yet been reached.

Q: Is there suspicion that Russian hackers may have tampered with votes?

A: No. Federal officials, including Homeland Security Secretary Jeh Johnson and FBI Director James Comey, have said that the decentralized nature of voting systems across the U.S. poses a difficult target for hackers.

"In our judgment, it would be very difficult to alter a ballot count in any one place and have a significant consequence,'' Johnson said in an interview last month with USA TODAY.

Q: What is the government doing to more definitively determine the extent of Russia's intrusions into the election process?

A: The Obama administration has ordered a review of attempts by foreign hackers to influence U.S. elections. The review, to be completed before President Obama leaves office on Jan. 20, is expected to examine the past three presidential elections.

“We may have crossed into a new threshold, and it is incumbent upon us to take stock of that, to review, to conduct some after-action, to understand what has happened and to impart some lessons learned,” Obama’s counterterrorism and homeland security adviser, Lisa Monaco, told reporters Friday.

Senate Majority Leader Mitch McConnell, R-Ky., said Monday that two Senate committees would investigate the CIA's new assessment of Russia's involvement.

He said the Senate Intelligence Committee and the Senate Armed Services Committee will conduct bipartisan reviews. Late Monday, a third Senate panel, the Foreign Relations Committee, also indicated it will review the matter.

"Obviously, any foreign breach of our cyber-security measures is disturbing and I strongly condemn any such efforts," McConnell told reporters Monday.

Republican leaders join outrage at Russia, will investigate hacks

Obama orders review of foreign attempts to hack U.S. election