Background Clinical trials remain a critical component of medical innovation. Evidence suggests that individuals’ political ideologies may impact their health behaviors. However, there is a paucity of literature examining the relationship between political ideologies and clinical trial knowledge and participation. Methods Study data were derived from Health Information National Trends Survey 5 Cycle 4 (n = 3300), which was conducted from February to June 2020. We used participants’ characteristics to estimate the prevalence of clinical trial knowledge and participation. We used multivariable logistic regressions to investigate whether political ideology had a significant impact on clinical trial knowledge and participation. Jack-knife replicate weights were applied for population-level estimates. Results Most participants were White (64.2%), earned above US$50,000 (62.4%), and lived in urban areas (88.0%). About 59.2% reported having some knowledge of clinical trials, and only 8.9% had ever been invited to participate in clinical trials. A total of 37.0%, 29.5%, and 33.5% of the population endorsed moderate, liberal, and conservative political viewpoints respectively. In the adjusted logistic regression analysis, compared to conservatives, liberals (adjusted odds ratio, 1.92; 95% confidence interval, 1.31–2.80) and moderates (adjusted odds ratio, 1.43; 95% confidence interval, 1.09–1.88) had significantly greater odds of having knowledge of clinical trials. Also, liberals had higher odds of receiving invitations to participate in clinical trials (odds ratio, 1.76; 95% confidence interval, 1.08–2.85; p = 0.023) and greater odds of trial participation (odds ratio, 3.90; 95% confidence interval, 1.47–10.33; p = 0.007) compared to moderates. Conclusions The mechanism underlying the higher rates of clinical trial invitations to liberals is unclear and requires further comprehensive investigation. Similarly, further qualitative studies are needed to understand the attributes that promote knowledge and increased likelihood of clinical trial participation among liberals. This will provide crucial insight to help design interventions that further involve conservatives and moderates in clinical trials and scientific enterprise.