While isolated incidents of illegal aliens voting in U.S. Elections have been documented, widespread or systematic illegal voting by noncitizens is not supported by credible evidence.
Illegal aliens are voting in elections.

Democrats vote overwhelmingly to allow illegal aliens to continue voting in key district - U.S. Representative
Source: pfluger.house.gov
Key Evidence
Nineteen foreign nationals were indicted for illegally voting in the 2016 elections, showing isolated cases do exist.
ice.govice.govArchived: 19 foreign nationals indicted for illegally voting in 2016 elections
FactCheck.org found no credible evidence supporting claims of massive illegal voting by noncitizens despite such claims being made publicly.
factcheck.orgfactcheck.orgMusk's Unsupported Claim to Have Unveiled Massive Illegal Voting by Noncitizens
Laws exist to prevent illegal voting by noncitizens, but enforcement and compliance vary.
haridopolos.house.govharidopolos.house.govCongressman Mike Haridopolos Votes to Prevent Illegal Immigrants from Voting in...
What the Evidence Shows
The claim that "illegal aliens are voting in elections" contains elements of truth but is often presented in a misleading way that exaggerates the scale and impact.
Documented Cases: There have been documented cases where noncitizens, including illegal aliens, have illegally voted in U.S. Elections. For example, law enforcement agencies have indicted some foreign nationals for illegal voting in past elections.ice.govice.govArchived: 19 foreign nationals indicted for illegally voting in 2016 elections
Scale and Impact: Despite these cases, comprehensive investigations and fact-checking organizations find no evidence of widespread or systemic illegal voting by noncitizens that would affect election outcomes.factcheck.orgfactcheck.orgMusk's Unsupported Claim to Have Unveiled Massive Illegal Voting by Noncitizens Claims of massive illegal voting often lack credible evidence and are sometimes politically motivated.
Legal Framework: Federal laws prohibit noncitizens from voting in federal elections, with penalties for violations.haridopolos.house.govharidopolos.house.govCongressman Mike Haridopolos Votes to Prevent Illegal Immigrants from Voting in... However, enforcement challenges exist, and some local jurisdictions have allowed noncitizen voting in limited local elections, which is a separate issue.
pfluger.house.govpfluger.house.govDemocrats vote overwhelmingly to allow illegal aliens to continue voting in key...
Election Integrity Efforts: Various political actors advocate for stricter laws and enforcement to prevent any illegal voting by noncitizens.heritage.orgheritage.orgIllegal Aliens Are Still Voting in Our Elections+1 more However, the presence of laws does not guarantee perfect compliance.
Misinformation Risk: Some sources or claims conflate isolated incidents with systemic problems or use anecdotal evidence to imply widespread fraud without substantiation.ricochet.comricochet.comHow Are Illegal Aliens Voting in U.S. Elections?
armstrongeconomics.comarmstrongeconomics.comIllegal Aliens Voting?
In summary, while illegal voting by noncitizens has occurred in isolated instances, the claim that illegal aliens are broadly voting in U.S. Elections is misleading without context about scale and evidence.