In June of 2019, the New York Times reported:
WASHINGTON — A raft of legislation intended to better secure United States election systems after what the special counsel, Robert S. Mueller III, called a “sweeping and systematic” Russian attack in 2016 is running into a one-man roadblock in the form of the Senate majority leader, Mitch McConnell of Kentucky.
The bills include a Democratic measure that would send more than $1 billion to state and local governments to tighten election security, but would also demand a national strategy to protect American democratic institutions against cyberattacks and require that states spend federal funds only on federally certified “election infrastructure vendors.” A bipartisan measure in both chambers would require internet companies like Facebook to disclose the purchasers of political ads.
Another bipartisan Senate proposal would codify cyberinformation-sharing initiatives between federal intelligence services and state election officials, speed up the granting of security clearances to state officials and provide federal incentives for states to adopt paper ballots.
But even bipartisan coalitions have begun to crumble in the face of the majority leader’s blockade. Mr. McConnell, long the Senate’s leading ideological opponent to federal regulation of elections, has told colleagues in recent months that he has no plans to consider stand-alone legislation on the matter this term, despite clamoring from members of his own conference and the growing pressure from Democrats who also sense a political advantage in trying to make the Republican response to Russia’s election attack look anemic.
https://www.nytimes.com/2019/06/07/us/politics/election-security-mitch-mcconnell.html
According to more recent reporting from the New York Times:
In opposing the other election overhauls, Mr. McConnell has criticized them as Democratic attempts to gain a partisan advantage. He also argued that many new protections had already been put in place since 2016, and that the 2018 election showed that they were working.
“The Trump administration has made enormous strides to help states secure their elections without giving Washington new power to push the states around,” Mr. McConnell said.
https://www.nytimes.com/2019/09/19/us/politics/mcconnell-election-security.html
ABC News reporting includes a quote from the Senate Majority leader:
But McConnell said Democrats were just trying to make political hay on the heels of the Mueller testimony in their attempt to bring up a House bill that would mandate the use of paper ballots in states' election systems and provide additional funding to the federal, nonpartisan Election Assistance Commission.
"This is partisan legislation from the Democratic House of Representatives," McConnell said, noting that the bill garnered just one GOP vote in that chamber and was designed to give Democrats the political upper-hand.
"It's very important that we maintain the integrity and security of our elections in our country," the GOP leader said, but he added, "any Washington involvement in that task needs to be undertaken with extreme care, extreme care and on a thoroughly bipartisan basis. Obviously this legislation is not that. It's just a highly partisan bill from the same folks who spent two years hyping up a conspiracy theory about President Trump and Russia."
As evidenced by the first quote, the Democrats have come up with different election-security measures which have not been brought to the Senate floor with Republicans, at least through Senate Majority Leader Mitch McConnell per the second quote, criticizing them for being partisan.
Has he, the broader Republican Party or others (e.g. in academia) elaborated what exactly is partisan about (some of) these proposals? Given the severity of election security (e.g. considering the mueller-investigation) it seems they would have to have good reasons for not working on these proposals.
Answers could be based on statements directly pointing out what's partisan or perhaps based on alternative proposals on election security by pointing out differences between proposals on similar areas of election security.
